100+ Codingal Interview Questions and Answers

The strategy is to always subtract the number chosen by the friend from 4 to ensure reaching 16 first.

• Start with 20 and subtract the number chosen by the friend from 4.

• Continue this strategy until reaching 16 before the friend reaches 17-19.

• Ensure the friend ends up at any number between 17 to 19 before reaching 16.

Conditions for overflow and steady state in a tank with inflow and outflow

• Overflow occurs when the inflow rate is greater than the outflow rate

• Steady state is achieved when the inflow rate equals the outflow rate

• Overflow can be prevented by adjusting the inflow rate or increasing the outflow rate

• Steady state can be maintained by balancing the inflow and outflow rates

The most probable number on the last toss is 6.

• The probability of getting a sum of 100 or more is highest when the sum is 99.

• The last toss will be made to reach the sum of 100, so the most probable number is the one that will take the sum closest to 100.

• The sum of 94 can be achieved by rolling a 6 on the last toss, which is the most probable number.

Count number of ways to reach 20 on number line starting from 0 in steps of 1 or 2. Derive recursive formula for n+1.

• Use dynamic programming to count number of ways for each step.

• For each step, number of ways is sum of number of ways for previous 1 or 2 steps.

• Recursive formula: ways[n+1] = ways[n] + ways[n-1]

The goal is to find the maximum sum of a non-empty contiguous subarray within an array of integers.

• Iterate through the array and keep track of the maximum sum of subarrays encountered so far.

• Use Kadane's algorithm to efficiently find the maximum subarray sum.

• Consider edge cases like all negative numbers in the array.

• Example: For input [1, -3, 4, -2, -1, 6], the maximum subarray sum is 7 (subarray [4, -2, -1, 6]).

Go second. The probability of winning is higher when going second.

• The probability of winning when going first is (1/n+1), while the probability of winning when going second is (n/n+1)

• This is because the first player has a chance of drawing the black ball on their turn, while the second player has a chance of drawing the black ball on their turn or the first player's turn

• For example, if there are 10 red balls and 1 black ball, the probability of winning when going first is 1/1...read more

Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.

• Implement a doubly linked list to keep track of the order of keys based on their recent usage.

• Use a hashmap to store key-value pairs for quick access.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Update the order of keys in the linked list whenever a key is accessed or inserted.

Find the shortest path in a binary matrix from a source cell to a destination cell consisting only of 1s.

• Use Breadth First Search (BFS) algorithm to find the shortest path.

• Keep track of visited cells to avoid revisiting them.

• Calculate the path length by counting the number of 1s in the path.

• Return -1 if no valid path exists.

There are (N-1)! ways to eat chocolates from left to right.

• The first chocolate can be chosen in N ways, the second in (N-1) ways, and so on.

• However, since the order of chocolates eaten matters, we need to divide by the number of ways to order N chocolates, which is N!.

• Therefore, the total number of ways to eat chocolates is (N-1)!

• For example, if N=4, there are 3! = 6 ways to eat the chocolates.

Compute working days using given functions f, g, and h.

• To compute the 3rd working day, apply function g three times to function f.

• To compute the 2nd working day of the previous month, apply function h to function f, then apply function g twice.

• To compute the 4th working day of the next month, apply function g four times to function f.

Probability of winning a dice game where the one with lesser number wins.

• The probability of winning depends on the number of sides on the dice.

• If the dice has an odd number of sides, the probability of winning is higher for the second player.

• If the dice has an even number of sides, the probability of winning is equal for both players.

Probability of a randomly dropped rod of length L intersecting a line on a 2D plane with infinite parallel, vertical lines.

• The probability depends on the length of the rod L.

• The probability can be calculated using geometric probability.

• The probability is 1 - (2L - 1) / infinity.

• For example, if L = 1, the probability is 0.5.

• If L = 2, the probability is 0.75.

Flip the coin twice and consider the outcome as follows.

• Flip the coin twice and consider the outcome as follows:

• - If both flips are heads or both are tails, discard and flip again.

• - If the first flip is heads and the second is tails, consider it as heads.

• - If the first flip is tails and the second is heads, consider it as tails.

• This method ensures a 50-50 chance of getting either heads or tails.

• Alternatively, use a physical method to balance the weight distribution of the coi...read more

Probability of a rod of length L covering an integer on a number line.

• The probability depends on the length of the rod and the distance between adjacent integers on the number line.

• If the length of the rod is less than the distance between adjacent integers, the probability is zero.

• If the length of the rod is greater than or equal to the distance between adjacent integers, the probability is (L - d)/d, where d is the distance between adjacent integers.

• The probability can be c...read more

No, it is not possible for each person to give gifts to 3 people and receive a gift from them in a party of 9 people.

• In this scenario, each person would need to receive 3 gifts, which is not possible if there are only 9 people.

• This scenario would be possible if there were at least 10 people at the party.

• In general, for a party of n people, each person can give gifts to n-1 people and receive gifts from n-1 people.

Algorithm to search for a number in an n x n matrix with sorted rows and columns.

• Start from the top-right corner of the matrix

• If the current element is greater than the target, move left

• If the current element is less than the target, move down

• Repeat until the target is found or the bottom-left corner is reached

The price of a barrier option is generally less than a normal option.

• Barrier options have a condition that must be met for the option to be activated, which reduces the likelihood of the option being exercised.

• This reduced likelihood of exercise means that barrier options are generally cheaper than normal options.

• However, the price of a barrier option can vary depending on the specific conditions and terms of the option.

• For example, a knock-in barrier option may be more expen...read more

What is the most likely value of the last roll in a game where a die is rolled until the sum of all rolls is at least 100?

• The last roll must be at least 4 to reach a sum of 100

• The probability of rolling a 4, 5, or 6 is 1/2

• The most likely value of the last roll is 4 or 5

The Convex Hull is the smallest convex polygon that encloses all given points.

• Sort the points based on their x-coordinate.

• Find the upper hull by starting from the leftmost point and moving clockwise.

• Find the lower hull by starting from the rightmost point and moving counterclockwise.

• Combine the upper and lower hulls to form the convex hull.

You can buy fuel from us through our fuel card program.

• We offer a fuel card program that allows you to purchase fuel from our network of stations.

• Our fuel card program offers discounts and rewards for frequent users.

• You can easily track your fuel expenses and usage through our online portal.

• We also offer customized fuel solutions for businesses and fleets.

• Our fuel is high-quality and meets all industry standards.

Increasing stock volatility increases the price of a call option.

• Higher volatility means higher potential for the stock to move in the option holder's favor, increasing the option's value

• The option's delta and gamma will also increase with higher volatility

• Example: If a call option on a stock with a strike price of $50 has a premium of $2 when the stock has a volatility of 20%, increasing the volatility to 30% may increase the premium to $2.50 or higher

Find the magic number in a sorted array where value and index are same.

• Iterate through the array and check if the value and index are same

• If found, return the value

• If not found, return -1

CPI stands for Consumer Price Index, not the same as Grade Point Average (GPA).

• CPI is a measure of the average change over time in the prices paid by urban consumers for a market basket of consumer goods and services.

• It is used to track inflation and price changes in the economy.

• GPA, on the other hand, is a measure of academic performance and represents a student's average grade point across courses.

• CPI and GPA are completely different concepts and have no relation to each ot...read more

Expected number of tosses of a fair coin to get 3 consecutive heads.

• The probability of getting 3 consecutive heads is 1/8

• The expected number of tosses to get 3 consecutive heads is 14

• This can be calculated using the formula E(X) = 2^k + 2^(k-1) + 2^(k-2) + ... + 2^2 + 2^1 + 2^0, where k is the number of consecutive heads required

A call option is a financial contract that gives the buyer the right, but not the obligation, to buy an underlying asset at a predetermined price within a specified time period.

• Call options are bought by investors who believe that the price of the underlying asset will rise in the future.

• The buyer of a call option pays a premium to the seller for the right to buy the asset at a predetermined price, known as the strike price.

• If the price of the asset rises above the strike pri...read more

The price of a call option is calculated using the Black-Scholes model which takes into account the underlying asset price, strike price, time to expiration, risk-free interest rate, and volatility.

• Determine the current price of the underlying asset

• Determine the strike price of the option

• Determine the time to expiration of the option

• Determine the risk-free interest rate

• Determine the volatility of the underlying asset

• Plug these values into the Black-Scholes model to calculate ...read more

Algorithm to find largest common subarray of two arrays of size n

• Create a 2D array to store the lengths of common subarrays

• Traverse both arrays and fill the 2D array with lengths of common subarrays

• Find the maximum length and its corresponding ending index in the 2D array

• Use the ending index to retrieve the largest common subarray from either of the arrays

The problem involves finding an element in a matrix that is sorted both row-wise and column-wise.

• Start from the top-right corner of the matrix

• Compare the target element with the current element

• If the target is smaller, move left; if larger, move down

• Repeat until the target is found or the matrix boundaries are crossed

Efficient ways to implement product and summation of n numbers with limitations.

• For summation, use a loop or built-in functions like sum() or reduce().

• For product, use a loop or built-in functions like prod() or reduce().

• Limitations include overflow errors for large numbers and memory constraints for very large arrays.

• Using parallel processing or vectorization can improve efficiency.

• Consider using data structures like binary trees or prefix sums for faster calculations.

There are infinite ways to sort an infinite array with varying complexities.

• Sorting algorithms like QuickSort, MergeSort, HeapSort, etc. can be used to sort the array.

• The time complexity of sorting algorithms varies from O(n log n) to O(n^2).

• The space complexity also varies depending on the algorithm used.

• Sorting an infinite array is not practical, so it is usually done in chunks or using parallel processing.

• The sorting order can be ascending or descending based on the requir...read more

Options are financial contracts that give the buyer the right, but not the obligation, to buy or sell an underlying asset at a predetermined price.

• Options can be used for hedging or speculation

• There are two types of options: call options and put options

• Call options give the buyer the right to buy the underlying asset at a predetermined price, while put options give the buyer the right to sell the underlying asset at a predetermined price

• Options have expiration dates and strik...read more

Number of ways to jump n stairs if a person can climb 1 or 2 stairs.

• Use dynamic programming to solve the problem.

• The number of ways to jump n stairs is equal to the sum of ways to jump n-1 stairs and ways to jump n-2 stairs.

• Base cases: if n=0, return 1 and if n=1, return 1.

Searching an element in a sorted 2D matrix

• Start from the top-right corner or bottom-left corner

• Compare the target element with the current element

• Move left or down if the target is smaller or move right or up if the target is larger

Efficient algorithms for calculating Fibonacci's sequence

• Use dynamic programming to avoid redundant calculations

• Implement matrix exponentiation to reduce time complexity to O(log n)

• Use memoization to store previously calculated values

• Iterative approach using constant space complexity

• Binet's formula for direct calculation of nth Fibonacci number

Replace each node in a binary tree with its depth starting from root as 0.

• Traverse the binary tree in inorder fashion and update each node's data with its depth.

• Start with depth 0 for the root node and increment the depth as you go down the tree.

• Handle cases where nodes do not have left or right child by taking -1 in their place.

• Print the inorder traversal of the tree with updated node data representing the depth.

An LRU cache can be made using a doubly linked list and a hash map.

• Create a doubly linked list to store the cache items.

• Create a hash map to store the key-value pairs.

• When a new item is added, check if the cache is full. If it is, remove the least recently used item from the linked list and hash map.

• When an item is accessed, move it to the front of the linked list.

• When an item is removed, remove it from both the linked list and hash map.

Implement a function to delete a node from a linked list at a specified position.

• Traverse the linked list to find the node at the specified position.

• Update the pointers of the previous and next nodes to skip the node to be deleted.

• Handle edge cases such as deleting the head or tail of the linked list.

• Ensure to free the memory of the deleted node to avoid memory leaks.

Find integer solutions of x^y=y^x.

• If x=y, then x^y=y^x=1

• If x

• If x>y, then x^y>y^x

• Only solution is (2,4) and (4,2)

• Use logarithms to prove

Hedge funds are actively managed investment funds that use various strategies to generate high returns, while private equity firms invest in private companies and aim to increase their value.

• Hedge funds are open to a wider range of investors than private equity funds

• Hedge funds use leverage to increase returns, while private equity firms use debt to finance acquisitions

• Hedge funds have a shorter investment horizon than private equity firms

• Private equity firms typically take a...read more

Find the longest palindromic substring in a given string, returning the rightmost one if multiple substrings are of the same length.

• Use dynamic programming to check for palindromes within the string.

• Start by checking for palindromes of length 1 and 2, then expand to longer substrings.

• Keep track of the longest palindromic substring found so far and return the rightmost one if multiple substrings are of the same length.

The problem is to connect N ropes of different lengths into one rope with minimum cost.

• Sort the array of rope lengths in ascending order.

• Initialize a variable to keep track of the total cost.

• While there are more than one rope remaining, take the two shortest ropes and connect them.

• Add the cost of connecting the two ropes to the total cost.

• Replace the two shortest ropes with the connected rope.

• Repeat the above steps until only one rope remains.

• Return the total cost.

The task is to modify a given matrix such that if any element in a row or column is 0, then make all elements in that row and column 0.

• Iterate through the matrix and keep track of rows and columns that contain 0s

• After the first iteration, iterate through the tracked rows and columns and set all elements to 0

• Handle the case where the first row or column contains 0 separately

• To solve with O(1) space complexity, use the first row and first column of the matrix to track the rows ...read more

Design a newspaper subscription system

• Create a user registration system

• Allow users to select subscription plan and payment method

• Provide options for delivery frequency and start/end dates

• Send reminders for subscription renewal

• Allow users to modify or cancel subscription

• Track subscription history and payment records

Serialization and deserialization of an N-ary tree involves converting the tree into a sequence of bits and reconstructing the original tree from this format.

• Serialize the N-ary tree by traversing it in level order and representing each node and its children using a space-separated sequence of integers.

• Deserialize the serialized tree by parsing the input sequence and reconstructing the tree structure based on the provided format.

• Use a queue data structure for deserialization ...read more

Design a constant time data structure for key-value mappings with operations like INSERT, DELETE, SEARCH, GET, GET_SIZE, and IS_EMPTY.

• Use a hash table to achieve constant time complexity for operations.

• Implement INSERT, DELETE, SEARCH, GET, GET_SIZE, and IS_EMPTY functions.

• Ensure key is a string and value is a positive integer.

• Return appropriate results based on the operation type.

• Handle edge cases like key not found or data structure being empty.

The task is to determine if two strings are similar based on the given conditions.

• Check if the strings are equal, if yes, return 1

• Divide both strings into two parts and check if any combination satisfies the similarity condition

• If none of the conditions hold true, return 0

Count the number of occurrences of a given word in a 2D grid by moving in all eight possible directions.

• Iterate through each cell in the grid and start searching for the word from that cell in all eight directions.

• Keep track of the number of occurrences found while searching.

• Handle edge cases like word length exceeding grid dimensions or starting from out-of-bounds cells.

Given a Unix-style directory path, simplify it by following certain rules and return the simplified path.

• Use a stack to keep track of directories while iterating through the input path.

• Handle cases for '.', '..', and multiple slashes appropriately.

• Return the simplified path by joining the directories in the stack with '/' separator.

Binary Search Tree is a data structure where each node has at most two children, with left child less than parent and right child greater.

• Nodes have at most two children - left and right

• Left child is less than parent, right child is greater

• Allows for efficient searching, insertion, and deletion of elements

Count the number of positive integral pairs (X, Y) that satisfy the given equation.

• Iterate through all possible values of X and calculate corresponding Y to check if the equation is satisfied.

• Optimize the solution by considering the constraints and properties of the equation.

• Handle special cases like when N is 1 or when X and Y are equal.

• Use mathematical properties to reduce the number of calculations needed.

• Consider edge cases like when N is a prime number.

Matrix Word Search Problem - Find occurrences of a given word in all eight possible directions within a matrix.

• Iterate through each cell in the matrix and check for the starting character of the word.

• For each occurrence of the starting character, check all eight directions for the complete word.

• Keep track of the coordinates of each character in the word for each occurrence found.

• Ensure boundaries are not crossed while searching in all directions.

• Output the coordinates of each...read more

The task is to find the shortest path of transformed 0s that connects two islands in a binary matrix.

• Identify the two islands in the binary matrix.

• Find the shortest path between the two islands by converting 0s to 1s.

• Output the minimal length of the bridge needed to connect the two islands.

The task is to determine the maximum profit that can be achieved by performing up to two buy-and-sell transactions on a given set of stock prices.

• Iterate through the array of stock prices and calculate the maximum profit that can be achieved by buying and selling at different points.

• Keep track of the maximum profit after the first transaction and the maximum profit overall by considering different combinations of buy and sell points.

• Ensure to sell the stock before buying agai...read more

Asset management is the process of managing and optimizing a company's assets to maximize their value and minimize risk.

• Asset management involves identifying, tracking, and evaluating assets

• It includes developing strategies to optimize asset performance and minimize risk

• Examples of assets that can be managed include financial investments, real estate, and equipment

• Asset management can be done in-house or outsourced to a third-party firm

Custodian banking involves holding and safeguarding financial assets on behalf of clients.

• Custodian banks provide services such as asset safekeeping, settlement of trades, and corporate actions processing.

• They also offer reporting and analytics to clients on their holdings and transactions.

• Examples of custodian banks include State Street, BNY Mellon, and J.P. Morgan.

• Custodian banking is important for institutional investors such as pension funds, mutual funds, and hedge funds...read more

The problem involves executing range sum and point update queries on an array using Fenwick Tree data structure.

• Use Fenwick Tree to efficiently handle range sum and point update queries.

• For range sum queries, calculate prefix sums and use them to compute the sum in the given range.

• For point update queries, update the Fenwick Tree accordingly to reflect the changes in the array.

• Ensure to handle the queries efficiently to meet the time constraints.

• Example: Given array [3, 2, 1,...read more

Given a binary matrix, maximize the score by toggling rows or columns to convert them to binary numbers and summing them up.

• Iterate through each row and column to calculate the score of toggling that row or column

• Keep track of the maximum score obtained by toggling rows or columns

• Return the maximum score obtained

Implement a function to solve a Sudoku puzzle by filling empty cells with valid numbers.

• Iterate through each empty cell and try filling it with a valid number (1-9) that satisfies Sudoku rules.

• Use backtracking to backtrack and try different numbers if a cell cannot be filled with a valid number.

• Check rows, columns, and 3x3 sub-grids to ensure each digit appears only once in each.

• Recursively solve the puzzle by filling empty cells until a valid solution is found.

Convert Morse code to alphanumeric code using a predefined table.

• Iterate through the morse code string and convert each morse code to its corresponding alphanumeric character using the given table.

• Join the converted characters to form the final alphanumeric string.

• Handle spaces between morse code characters by adding a space in the final alphanumeric string.

Private equity is a type of investment where funds are raised from investors to acquire or invest in companies that are not publicly traded.

• Private equity firms typically buy a controlling stake in a company and then work to improve its operations and profitability before selling it for a profit.

• Private equity investments are typically made in mature companies with a proven track record of success.

• Private equity firms may also invest in distressed companies with the goal of t...read more

The task is to find the total number of ways to make change for a specified value using given denominations.

• Create a dynamic programming table to store the number of ways to make change for each value up to the specified value.

• Iterate through each denomination and update the table accordingly.

• The final answer will be the value in the table at the specified value.

• Consider edge cases such as when the specified value is 0 or when there are no denominations provided.

Given a string with wildcard characters, determine if it can be transformed to match another string under given rules.

• Iterate through both strings simultaneously, handling wildcard characters '?' and '*' accordingly.

• Use dynamic programming to keep track of matching characters.

• Handle '*' by considering all possibilities of matching sequences.

• Return true if at the end both strings match, false otherwise.

The task is to determine a player's leaderboard rank for each game score based on given leaderboard and game scores.

• Iterate through each game score and compare it with leaderboard scores to determine the rank.

• Use a hashmap to store the leaderboard scores and their corresponding ranks.

• Handle cases where multiple players have the same score and share the same rank.

• Return an array of ranks for each game score.

The task is to flatten a multi-level linked list into a singly linked list and return the head of the modified linked list.

• Traverse the linked list and keep track of nodes with child pointers

• Flatten the child linked list and merge it with the main linked list

• Update the 'next' pointers to create a singly linked list

• Return the head of the modified linked list

Design a HashSet data structure with add, contains, and remove functions.

• Implement a HashSet using an array and handling collisions using chaining or open addressing.

• Use a hash function to map values to indices in the array.

• For add function, insert the value at the hashed index.

• For contains function, check if the value exists at the hashed index.

• For remove function, delete the value at the hashed index and return it, or return -1 if not found.

Determine reachability between all pairs of vertices in a directed graph.

• Use Floyd Warshall algorithm to find transitive closure of the graph.

• Initialize a V x V matrix with 1s on the diagonal and 0s elsewhere.

• Update matrix by checking if there is a path from i to j through k.

• Repeat the process for all vertices to get the transitive closure matrix.

Given 'N' types of umbrellas with different capacities, find the minimum number of umbrellas required to shelter exactly 'M' people.

• Iterate through the umbrella capacities and try to cover 'M' people using the minimum number of umbrellas.

• Sort the umbrella capacities in descending order to optimize the solution.

• If it is not possible to cover 'M' people exactly, return -1.

Split array into two subsets with minimum absolute difference between their sums.

• Use dynamic programming to find the minimum absolute difference between the sums of two subsets.

• Iterate through all possible sums of subsets and find the minimum difference.

• Consider each element either being included in the first subset or the second subset.

• Keep track of the minimum absolute difference found so far.

• Return the minimum absolute difference between the sums of the two subsets.

The task is to distribute candies to students based on their performance while minimizing the total candies distributed.

• Create an array to store the minimum candies required for each student.

• Iterate through the students' ratings array to determine the minimum candies needed based on the adjacent ratings.

• Consider both left-to-right and right-to-left passes to ensure fair distribution.

• Keep track of the total candies distributed and return the sum as the output.

Level order traversal of a binary tree is returned for each test case.

• Implement a function to perform level order traversal of a binary tree

• Use a queue data structure to keep track of nodes at each level

• Print the node values in level order traversal

Given finish times of horses, find fastest horse in specified lane ranges for multiple queries.

• Iterate through each query and find the minimum finish time within the specified range.

• Use a loop to process each test case and query efficiently.

• Ensure to handle edge cases like empty ranges or invalid inputs.

• Optimize the solution to handle large input sizes efficiently.

Given a binary tree, a target node, and an integer K, find all nodes at distance K from the target node.

• Traverse the binary tree to find the target node.

• Use BFS to traverse the tree from the target node to nodes at distance K.

• Keep track of the distance while traversing the tree.

• Return the values of nodes at distance K in any order.

Flatten a multi-level linked list into a singly linked list and return the head of the flattened list.

• Traverse the linked list in level order

• Use a stack to keep track of nodes with child pointers

• Merge the child nodes into the main list

Identify the celebrity at a party where one person knows everyone but is not known by anyone.

• Use a two-pointer approach to eliminate non-celebrities.

• Start with two pointers at the beginning and end, move them based on 'knows' results.

• If A knows B, A cannot be the celebrity; move A pointer. If A does not know B, B cannot be the celebrity; move B pointer.

• Repeat until only one person remains, check if this person is known by everyone and knows no one.

• Return the ID of the celebri...read more

The problem involves dividing an array into K subsets with equal sum.

• Use backtracking to try all possible combinations of dividing the array into K subsets.

• Keep track of the sum of elements in each subset and check if they are equal to the target sum.

• Optimize the backtracking algorithm by pruning branches that cannot lead to a valid solution.

• Consider edge cases such as empty array, negative numbers, and unequal division of elements.

• Ensure that the sum of all elements in the a...read more

Find pairs in a sorted doubly-linked list whose sum equals a given integer 'X'.

• Traverse the list from both ends to find pairs with sum equal to 'X'.

• Use two pointers approach to efficiently find the pairs.

• Handle cases where the sum is less than, equal to, or greater than 'X'.

Compute the area of the largest rectangle that can be formed within the bounds of a given histogram.

• Iterate through the histogram bars and maintain a stack to keep track of increasing heights.

• Calculate the area of the rectangle by considering the current height as the height of the rectangle and the width as the difference between the current index and the index at the top of the stack.

• Update the maximum area found so far and return it as the result.

Find the smallest substring in a given string that contains all characters from another string.

• Use a sliding window approach to find the smallest window in S that contains all characters in X.

• Keep track of the characters in X using a hashmap.

• Move the right pointer to expand the window until all characters in X are found, then move the left pointer to shrink the window while maintaining the condition.

• Return the smallest window found.

• Example: S = 'abdd', X = 'bd' -> Output: 'bd...read more

The task is to find the smallest number greater than the given number with the same set of digits.

• Iterate from right to left to find the first digit that can be swapped with a smaller digit to make the number greater.

• Swap this digit with the smallest digit to its right that is greater than it.

• Sort all digits to the right of the swapped digit in ascending order to get the smallest number.

Find the maximum sum of non-adjacent nodes in a binary tree.

• Use dynamic programming to keep track of the maximum sum at each node considering whether to include or exclude the current node.

• Recursively traverse the binary tree while keeping track of the maximum sum of non-adjacent nodes.

• Consider the cases where the current node is included in the sum or excluded from the sum to calculate the maximum possible sum.

Merge overlapping intervals and return sorted list of merged intervals.

• Identify overlapping intervals based on start and end times

• Merge overlapping intervals to form new intervals

• Sort the merged intervals in ascending order of start times

Given a string, find the longest palindromic substring, prioritizing the one with the smallest start index.

• Iterate through the string and expand around each character to find palindromes.

• Keep track of the longest palindrome found and its starting index.

• Return the longest palindromic substring with the smallest start index.

Sort an array of strings based on a new alphabetical order starting with a given character.

• Iterate through the array of strings and compare each string with the given character to determine the new order.

• Use a custom comparator function to sort the strings based on the new alphabetical order.

• Handle lowercase English alphabet characters and strings of varying lengths.

Reverse a linked list in groups of size K.

• Iterate through the linked list in groups of size K

• Reverse each group of nodes

• Handle cases where the number of elements in the last group is less than K

Calculate total area covered by overlapping rectangles given their coordinates.

• Iterate through each rectangle and calculate its area

• Check for overlaps between rectangles and calculate the overlapping area

• Sum up the areas of all rectangles and subtract the total overlapping area to get the final result

Determine if two nodes in a binary tree are cousins based on level and parent criteria.

• Traverse the tree to find the levels and parents of the given nodes.

• Check if the nodes are at the same level and have different parents.

• Return 'YES' if the nodes are cousins, 'NO' otherwise.

Determine the maximum number of roads that can be removed while ensuring a path exists for every pair of cities for two-wheeler and four-wheeler vehicles.

• Identify the type of road (two-wheeler, four-wheeler, or both) and its impact on the connectivity between cities.

• Consider the constraints provided in the input to optimize the solution.

• Remove roads strategically to maximize the number of roads removed while maintaining connectivity.

• If not all cities can be reached, return -1...read more

Count the total number of unique pairs in an array whose elements sum up to a given value.

• Use a hashmap to store the frequency of each element in the array.

• Iterate through the array and for each element, check if (Sum - element) exists in the hashmap.

• Increment the count of pairs if the complement exists in the hashmap.

Find the Lowest Common Ancestor (LCA) of two nodes in a Binary Search Tree (BST).

• Traverse the BST from the root node to find the LCA of nodes P and Q.

• Compare the values of nodes P and Q with the current node's value to determine the LCA.

• If both nodes are on the same side of the current node, move to that side; otherwise, the current node is the LCA.

• Handle cases where one node is the ancestor of the other or when one of the nodes is the current node.

The minimum number of swaps required to sort a given array of distinct elements in ascending order.

• Use a graph-based approach to find cycles in the array

• Count the number of swaps needed to fix each cycle

• Sum up the swaps needed for all cycles to get the total minimum swaps

Find the number of ways a given number can be expressed as the sum of two or more consecutive natural numbers.

• Use a sliding window approach to iterate through all possible consecutive sums.

• Keep track of the sum of the current window and adjust the window size accordingly.

• Count the number of valid consecutive sum representations of the given number.

• Example: For N = 9, valid representations are 2 + 3 + 4 and 4 + 5, so the output is 2.

The goal is to minimize the difference between the maximum and minimum elements of an array by adjusting each element by a given value.

• Iterate through each test case and calculate the minimum possible difference between the maximum and minimum elements after modifications.

• For each element in the array, consider increasing or decreasing it by the given value K to minimize the overall difference.

• Return the calculated minimum difference for each test case.

The minimum number of platforms needed at a railway station to avoid train waiting times is determined based on arrival and departure times.

• Sort the arrival and departure times in ascending order.

• Iterate through the times and keep track of the number of platforms needed at any given time.

• Update the minimum number of platforms needed as you iterate through the times.

• Return the minimum number of platforms needed.

The total number of unique rectangles that can be formed in a grid with M rows and N columns.

• The total number of unique rectangles can be calculated using the formula: (M * (M + 1) / 2) * (N * (N + 1) / 2)

• Each rectangle can be formed by selecting two rows and two columns from the grid

• For example, for a grid with 3 rows and 4 columns, the total number of unique rectangles is 60