7000+ Software Developer Interview Questions and Answers

Find the maximum sum of any contiguous subarray within an array of integers.

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

• At each index, decide whether to include the current element in the subarray or start a new subarray.

• Use Kadane's algorithm to efficiently find the maximum subarray sum in O(N) time complexity.

Determine the minimum number of platforms needed at a railway station based on arrival and departure times of trains.

• Sort the arrival and departure times in ascending order.

• Use two pointers to keep track of overlapping schedules.

• Increment the platform count when a new train arrives before the previous one departs.

• Return the maximum platform count needed.

Merge two sorted arrays into one sorted array in place.

• Iterate from the end of both arrays and compare elements to merge in place

• Use two pointers to keep track of the current position in each array

• Handle cases where one array is fully merged before the other

Calculate the Nth Fibonacci number efficiently using dynamic programming.

• Use dynamic programming to store and reuse previously calculated Fibonacci numbers.

• Start with base cases F(1) and F(2) as 1, then calculate subsequent Fibonacci numbers.

• Optimize the solution to avoid redundant calculations by storing intermediate results.

• Time complexity can be reduced to O(N) using dynamic programming.

• Example: For N = 5, the 5th Fibonacci number is 5.

The task is to find the intersection of two integer arrays/lists.

• Read the number of test cases

• For each test case, read the size and elements of the first array/list

• Read the size and elements of the second array/list

• Find the intersection of the two arrays/lists

• Print the intersection elements in the order they appear in the first array/list

Arrange numbers in a sequence in 'N' rows with increasing order and repeating after 9.

• Iterate through each test case and for each row, print numbers in increasing order with a loop.

• Keep track of the current number to print and reset to 1 after reaching 9.

• Handle formatting to align numbers correctly in each row.

• Ensure to print the correct number of rows based on the input 'N'.

Generate the first 'X' terms of a series 3 * N + 2, excluding multiples of 4.

• Iterate through numbers starting from 1 and check if 3 * N + 2 is not a multiple of 4.

• Keep track of the count of terms generated and stop when 'X' terms are found.

• Return the list of 'X' terms that meet the criteria.

• Example: For X = 4, the output should be [5, 11, 14, 17].

Given a matrix of coins, Alice and Bob have to collect maximum coins with certain conditions.

• Alice starts from top left corner and Bob starts from top right corner

• They can move to (i+1, j+1) or (i+1, j-1) or (i+1, j)

• They have to collect all the coins that are present at a cell

• If Alice has already collected coins of a cell, then Bob gets no coins if goes through that cell again

The task is to find the minimum cost required to connect all the ropes by summing their lengths.

• Iterate through the ropes and connect the two shortest ropes at each step to minimize cost

• Use a priority queue to efficiently find the shortest ropes

• Keep track of the total cost as you connect the ropes

• Example: For input [4, 3, 2, 6], connect 2 and 3 (cost 5), then connect 4 and 5 (cost 9), then connect 9 and 6 (cost 15) for a total cost of 29

Determine if it's possible to form a non-degenerate triangle using array elements as sides.

• Check if the sum of any two sides is greater than the third side to form a triangle.

• If any such combination exists, return 'YES'; otherwise, return 'NO'.

• Example: For input [3, 4, 5], sum of 3 + 4 > 5, so 'YES'. For [1, 10, 12, 30], no such combination exists, so 'NO'.

Implement Fenwick Tree to handle range sum and point update queries on an array.

• Implement Fenwick Tree data structure to efficiently handle range sum and point update queries.

• For range sum queries, use prefix sum technique to calculate the sum of elements in the given range.

• For point update queries, update the Fenwick Tree structure accordingly.

• Handle each query type separately and output the required results.

• Ensure to follow the constraints provided in the problem statement.

Determine the minimum number of pre-processing moves required to make two strings equal by swapping characters and replacing characters in one string.

• Iterate through both strings simultaneously and count the number of characters that need to be swapped.

• Consider all possible swaps and replacements to find the minimum number of pre-processing moves.

• If the lengths of the strings are different, it's impossible to make them equal.

• Handle edge cases like empty strings or strings wit...read more

The task is to find all distinct triplets in an array that sum up to a specified number.

• Iterate through all possible triplets using three nested loops.

• Check if the sum of the triplet equals the target sum.

• Print the triplet if found, else print -1.

• Handle duplicate triplets by skipping duplicates during iteration.

Exception is a runtime error that can be handled, while error is a severe issue that cannot be handled.

• Exceptions are caused by the program logic, while errors are caused by external factors like hardware failure or network issues.

• Exceptions can be caught and handled using try-catch blocks, while errors require fixing the underlying issue.

• Example of exception: NullPointerException. Example of error: Out of Memory Error.

• To solve errors in code deployment, identify the root cau...read more

Reverse the order of elements in an array and display the reversed array.

• Iterate through the array from both ends and swap the elements until reaching the middle.

• Use a temporary variable to store the element being swapped.

• Print the reversed array after swapping all elements.

Count the number of arithmetic subarrays in an array.

• An arithmetic subarray has 3 or more elements with the same difference between consecutive elements.

• Loop through the array and check for all possible subarrays with 3 or more elements.

• If the difference between consecutive elements is the same, increment the count.

• Return the count for each test case.

Implement a function to find all palindromic numbers from 1 to N.

• Iterate from 1 to N and check if each number is a palindrome

• Use string manipulation to check for palindromes

• Consider edge cases like single-digit numbers and 11

Implement a wildcard pattern matching algorithm to determine if a given wildcard pattern matches a text string completely.

• Create a recursive function to match the pattern with the text character by character

• Handle cases for '?' and '*' characters in the pattern

• Keep track of the current position in both pattern and text strings

• Return 'True' if the pattern matches the text completely, otherwise return 'False'

Compute the number of valid permutations of integers from 0 to N-1 such that at least K positions satisfy ARR[I] = I.

• Use dynamic programming to solve the problem efficiently.

• Consider the cases where K is equal to N or N-1 separately.

• Modulo the result by 10^9 + 7 to avoid overflow issues.

The question asks to find the total amount of rainwater that can be trapped in the given elevation map.

• Iterate through the array and find the maximum height on the left and right side of each bar.

• Calculate the amount of water that can be trapped on each bar by subtracting its height from the minimum of the maximum heights on both sides.

• Sum up the amount of water trapped on each bar to get the total amount of rainwater trapped.

Check if two strings are permutations of each other.

• Create character frequency maps for both strings.

• Compare the frequency maps to check if they are permutations.

• Handle edge cases like empty strings or strings of different lengths.

The task is to determine if a given singly linked list forms a cycle or not.

• A cycle occurs when a node's next points back to a previous node in the list.

• To solve this problem, we can use the Floyd's Cycle-Finding Algorithm.

• The algorithm uses two pointers, one moving at a normal pace and the other moving twice as fast.

• If there is a cycle, the fast pointer will eventually catch up to the slow pointer.

• If the fast pointer reaches the end of the list (i.e., it encounters a null no...read more

Implement a search function to find a specified integer in a rotated sorted array.

• Implement a binary search algorithm to find the target integer in the rotated sorted array.

• Handle the cases where the target integer may lie in the left or right half of the array after rotation.

• Keep track of the mid element and adjust the search space based on the rotation.

• Return the index of the target integer if found, else return -1.

Find the intersection of two unsorted arrays while maintaining the order of elements from the first array.

• Iterate through the elements of the first array and check if they exist in the second array.

• Use a hash set to keep track of elements already seen in the second array for efficient lookup.

• Maintain the order of elements from the first array while finding the intersection.

• Handle duplicate elements in both arrays appropriately.

• Output the intersection elements in the order the...read more

The maximum number of balanced binary trees possible with a given height is to be counted and printed.

• A balanced binary tree is one in which the difference between the left and right subtree heights is less than or equal to 1.

• The number of balanced binary trees can be calculated using dynamic programming.

• The number of balanced binary trees with height 'H' can be obtained by summing the product of the number of balanced binary trees for each possible left and right subtree hei...read more

Find the greatest common divisor (GCD) of two given numbers 'X' and 'Y'.

• Iterate from 1 to the minimum of X and Y, check if both X and Y are divisible by the current number, update GCD if true

• Use Euclidean algorithm to find GCD: GCD(X, Y) = GCD(Y, X % Y)

• If one of the numbers is 0, the other number is the GCD

• Handle edge cases like when one of the numbers is 0 or negative

The task is to find the actual order of people in a queue based on their heights and the number of taller people in front of them.

• Iterate through the given arrays and create a list of tuples containing the height and number of taller people for each person.

• Sort the list of tuples in descending order of height and ascending order of the number of taller people.

• Create an empty result list and insert each tuple into the result list at the index specified by the number of taller ...read more

Sort an array of 0s, 1s, and 2s in linear time with a single scan approach.

• Use three pointers to keep track of the positions of 0s, 1s, and 2s in the array.

• Iterate through the array once and swap elements based on their values and the pointers.

• After the single scan, the array will be sorted in place with 0s, 1s, and 2s in order.

The task is to determine if it is possible to select three nodes from a binary tree such that their sum equals a given value.

• Traverse the binary tree and store all the node values in an array

• Use three nested loops to iterate through all possible combinations of three nodes

• Check if the sum of the three nodes equals the given value

• If a valid combination is found, return True

• If no valid combination is found, return False

Given an encrypted string with repeated substrings represented by counts, find the K'th character of the decrypted string.

• Parse the encrypted string to extract substrings and their counts

• Iterate through the substrings and counts to build the decrypted string

• Track the position in the decrypted string to find the K'th character

The task is to find the subarray with the maximum sum in a given array.

• Iterate through the array and keep track of the current sum and maximum sum seen so far.

• If the current sum becomes negative, reset it to 0 as it won't contribute to the maximum sum.

• Compare the maximum sum with the sum of the current subarray to update the result.

• Handle cases where all elements are negative by returning the maximum element in the array.

• Consider edge cases like empty array or array with only...read more

Find the missing integer in binary form from an array of unique binary strings.

• Iterate through the array of binary strings and convert each string to its decimal equivalent.

• Calculate the sum of all integers from 0 to N using the formula (N * (N + 1)) / 2.

• Subtract the sum of the integers represented by the binary strings from the total sum to find the missing integer.

• Convert the missing integer to binary form and return it as a string without leading zeros.

Determine if a valid balanced sequence can be achieved by replacing 'X's with suitable brackets.

• Iterate through the string and keep track of the count of opening and closing brackets.

• If at any point the count of closing brackets exceeds the count of opening brackets, return False.

• If all 'X's can be replaced to form a valid balanced sequence, return True.

Yes, this can be achieved by using a two-pointer approach to rearrange the array in-place with O(1) auxiliary space.

• Use two pointers, one starting from the beginning and one from the end of the array.

• Move the left pointer to the right until it encounters a positive number, and the right pointer to the left until it encounters a negative number.

• Swap the elements at the left and right pointers, and continue this process until the pointers meet.

• The resulting array will have all ...read more

The problem involves determining the minimum number of operations needed to make a binary string beautiful by ensuring it contains alternating 0s and 1s.

• Iterate through the binary string and count the number of operations needed to make it beautiful by flipping the bits as required.

• Keep track of the current bit and compare it with the next bit to determine if a flip operation is needed.

• Return the total number of operations needed for each test case.

The task is to sort an array in a wave form, where each element is greater than or equal to its adjacent elements.

• Iterate through the array and swap adjacent elements if they do not follow the wave pattern

• Start from the second element and compare it with the previous element, swap if necessary

• Continue this process until the end of the array

• Repeat the process for the remaining elements

• Return the sorted wave array

Given a binary matrix, find the distance of the nearest cell having 1 in the matrix for each cell.

• Use BFS to traverse the matrix and find the nearest cell having 1 for each cell.

• Initialize the output matrix with maximum possible distance.

• If the current cell has 1, distance is 0, else update distance based on the nearest cell having 1.

Print a triangle pattern of numbers based on given input 'N'.

• Iterate through each row and print the numbers in a centered and incremented manner

• Use nested loops to handle the alignment and incrementing of numbers

• Ensure to properly format the output with spaces for alignment

Given an array representing number of buses at each bus stop, determine how many buses originate from each stop.

• Iterate through the array and for each element, increment the count of buses originating from the corresponding bus stop.

• Use an array to store the count of buses originating from each stop.

• Remember to consider the constraint of 1-based indexing for bus stops.

Identify the length of the largest cycle in a maze represented by cells and an array of integers.

• Iterate through each cell and find the cycle length using DFS or Floyd's Tortoise and Hare algorithm.

• Handle self-cycles and cells with no exit by checking arr[i] = i and arr[i] = -1 respectively.

• Output the length of the largest cycle found or -1 if no cycles exist.

The longest continuous patch of a road repaired by a contractor is determined.

• Iterate through the updates and keep track of the start and end points of each patch

• Calculate the length of each patch and update the longest patch if necessary

• Return the start and end points of the longest patch

The problem is to assign aggressive cows to stalls in a way that maximizes the minimum distance between any two cows.

• Sort the array of stall positions in ascending order.

• Use binary search to find the largest minimum distance between cows.

• Check if it is possible to assign cows with this minimum distance by iterating through the sorted array.

• If it is possible, update the maximum distance and continue binary search for a larger minimum distance.

• If it is not possible, continue bi...read more

Determine if a person can reach an escape cell without encountering fire in a matrix.

• Check if the person can reach an escape cell without encountering fire by simulating the movement of the person and fire spread.

• If the person can reach an escape cell, return the time taken; otherwise, return -1.

• Consider the constraints and edge cases while implementing the solution.

Determine the maximum number of elements that can be made equal by performing at most K operations on an array of integers.

• Sort the array in non-decreasing order to easily identify the elements that need to be increased

• Calculate the difference between adjacent elements to determine the number of operations needed to make them equal

• Keep track of the total number of operations used and the maximum number of elements that can be made equal

Check if a permutation of one string is a substring of another string.

• Create a frequency map of characters in str1.

• Iterate through str2 with a window of size N and check if the frequency map matches.

• Return 'Yes' if a permutation is found, 'No' otherwise.