Top 250 Algorithms Interview Questions and Answers

Sort a list of people by their cities and states.

• Use a sorting algorithm like quicksort or mergesort.

• Create a custom comparator function that compares the city and state of each person.

• If two people belong to the same city and state, sort them by the...read more

Find the 2nd largest element in an array with the least time complexity.

• Sort the array in descending order and return the element at index 1.

• Initialize two variables to keep track of the largest and second largest elements.

• Iterate through the array a...read more

The task is to print two strings in an alternating sequence by indices.

• Iterate through both strings simultaneously and append characters alternately

• Handle the case where one string is longer than the other

• Use two pointers to keep track of the current...read more

The Longest Increasing Subsequence (LIS) problem is to find the length of the longest subsequence of a given sequence with increasing order.

• Use dynamic programming to solve the LIS problem efficiently.

• Maintain an array to store the length of the LIS ...read more

The task is to find a string of minimal length that includes every possible string of N digits with digits ranging from 0 to K as substrings.

• Generate all possible strings of N digits with digits from 0 to K

• Concatenate these strings in a way that all ...read more

The minimum number of characters needed to convert a string into a palindrome is the length of the string minus the length of the longest palindromic subsequence of the string.

• Find the longest palindromic subsequence of the given string.

• Subtract the ...read more

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 checkin...read more

The task is to find the kth smallest element of a merged array created by merging two sorted arrays.

• Merge the two sorted arrays into a single sorted array

• Return the kth element of the merged array

The task is to identify constellations shaped like vowels within a matrix filled with characters {#, *, .}.

• Iterate through the matrix to find 3x3 constellations shaped like vowels.

• Check for vowels 'A', 'E', 'I', 'O', 'U' in the constellations.

• Print t...read more

Calculate the number of mismatching bits between two given integers in their binary representation.

• Convert the integers to binary representation using bitwise operations.

• Count the number of differing bits by comparing the binary representations.

• Retur...read more

Find the maximum Manhattan distance from a 0-cell to its nearest 1-cell in a binary matrix.

• Iterate through the matrix to find all 0-cells and calculate their distances to nearest 1-cells using Manhattan distance formula

• Keep track of the maximum dista...read more

Use Sieve of Eratosthenes algorithm to optimize prime number generation.

• Implement Sieve of Eratosthenes algorithm to eliminate non-prime numbers

• Use boolean array to mark non-prime numbers

• Start with 2 and mark all its multiples as non-prime, then move...read more

Code for Fibonacci series up to 10

• Declare two variables to store the first two numbers of the series

• Use a loop to generate the next numbers in the series by adding the previous two

• Print the series up to 10

To reverse N cards, time complexity is O(N).

• The time complexity to reverse N cards is O(N).

• The algorithm needs to flip each card once, so the time complexity is linear.

• The time it takes to reverse all cards is directly proportional to the number of c...read more

Optimizing the listing of Restaurants on Swiggy involves using data-driven strategies to improve visibility, relevance, and user experience.

• Analyze user behavior and preferences to understand their needs and preferences

• Implement a ranking algorithm b...read more

Quick sort is a divide and conquer algorithm that sorts an array by partitioning it into two sub-arrays.

• Choose a pivot element from the array

• Partition the array around the pivot element

• Recursively apply the above steps to the sub-arrays

• Combine the so...read more

Reverse a number using recursion.

• Define a recursive function that takes the number as input

• Base case: if the number is less than 10, return the number

• Recursive case: return the last digit of the number concatenated with the result of calling the func...read more

Code to check if two words are anagrams

• Convert both words to lowercase

• Remove all spaces and punctuation

• Sort the characters in both words

• Compare the sorted words

There are several types of ML algorithms, including supervised learning, unsupervised learning, and reinforcement learning.

• Supervised learning: algorithms learn from labeled data to make predictions or classifications (e.g., linear regression, decisi...read more

Program to find even and odd number using lambda expression

• Create a list of numbers

• Use lambda expression to filter even and odd numbers

• Print the even and odd numbers

RPN is calculated using a postfix notation where operators come after the operands.

• RPN stands for Reverse Polish Notation

• Operators come after the operands in RPN

• RPN is evaluated using a stack data structure

• Example: 3 4 + 5 * = 35

• Example: 10 5 / 2 * =...read more

BFS and DFS are two popular graph traversal algorithms. BFS explores the graph level by level while DFS explores the graph depth by depth.

• BFS uses a queue data structure while DFS uses a stack or recursion.

• BFS is guaranteed to find the shortest path ...read more

Find the longest consecutive character path length for each character in a matrix given a string.

• Iterate through the matrix and for each character in the string, find the longest consecutive path in all 8 directions.

• Keep track of the current path len...read more

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...read more

Find longest increasing sequence in a matrix

• Iterate through each element in the matrix

• For each element, check its neighbors to find the longest increasing sequence

• Keep track of the longest sequence found so far

Use sliding window technique to find smallest subarray with k distinct values.

• Use a sliding window approach to keep track of the subarray with k distinct values.

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

• Slide the window to th...read more

Find the next smaller element for each element in an array.

• Iterate through the array from right to left and use a stack to keep track of elements.

• Pop elements from the stack until a smaller element is found or the stack is empty.

• If a smaller element ...read more