Wallero Technologies Interview Questions and Answers

Round duration - 30 minutes
Round difficulty - Medium

This was a MCQ round. 30 ques in 30 mins consisting of difficult quantitative aptitude questions were to be solved.

Round duration - 60 minutes
Round difficulty - Medium

In this test round, 2 coding questions were given. Either write the code or pseudo code

Q1. 
N Queens Problem
Given an integer N, find all possible placements of N queens on an N x N chessboard such that no two queens threaten each other.
Explanation:
A queen can attack another queen if they ar...read more
Ans. 
The N Queens Problem involves finding all possible placements of N queens on an N x N chessboard without threatening each other.
• Use backtracking algorithm to explore all possible configurations.

• Keep track of rows, columns, and diagonals to ensure queens do not threaten each other.

• Generate all valid configurations and print them out.
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Q2. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an array of 0s, 1s, and 2s in linear time complexity.
• Use three pointers to keep track of 0s, 1s, and 2s while traversing the array.

• Swap elements based on the values encountered to sort the array in-place.

• Time complexity should be O(N) and space complexity should be O(1).
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Round duration - 60 minutes
Round difficulty - Easy

This was a technical round with questions on DSA.

Q1. 
Reverse Words in a String: Problem Statement
You are given a string of length N. Your task is to reverse the string word by word. The input may contain multiple spaces between words and may have leading o...read more
Ans. 
Reverse words in a string while handling leading, trailing, and multiple spaces.
• Split the input string by spaces to get individual words

• Reverse the order of the words

• Join the reversed words with a single space in between
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Q2. 
Circular Linked List Detection
You are provided with the head of a linked list containing integers. Your task is to determine if the linked list is circular.
Note:
• A linked list is considered circula...read more
Ans. 
Detect if a given linked list is circular by checking if it forms a closed loop.
• Traverse the linked list using two pointers, one moving at double the speed of the other.

• If the two pointers meet at any point, the linked list is circular.

• If the faster pointer reaches the end of the list (NULL), the linked list is not circular.
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Round duration - 30 minutes
Round difficulty - Easy

HR round with typical behavioral problems.

Round duration - 40 minutes
Round difficulty - Medium

Asked about time complexity of algorithm, puzzles, DBMS, cutting edge technologies etc. What are indexes?

Q1. 
Flip Bits Problem Explanation
Given an array of integers ARR of size N, consisting of 0s and 1s, you need to select a sub-array and flip its bits. Your task is to return the maximum count of 1s that can b...read more
Ans. 
Given an array of 0s and 1s, find the maximum count of 1s by flipping a sub-array at most once.
• Iterate through the array and keep track of the maximum count of 1s obtained by flipping a sub-array.

• Consider flipping a sub-array from index i to j and calculate the count of 1s in the resulting array.

• Return the maximum count of 1s obtained by flipping a sub-array at most once.
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Round duration - 20 minutes
Round difficulty - Medium

Asked 1 standard algorithm

Q1. 
Number of Islands Problem Statement
You are provided with a 2-dimensional matrix having N rows and M columns, containing only 1s (land) and 0s (water). Your goal is to determine the number of islands in t...read more
Ans. 
Count the number of islands in a 2D matrix of 1s and 0s.
• Iterate through the matrix and perform depth-first search (DFS) to find connected 1s.

• Mark visited cells to avoid redundant traversal.

• Increment island count whenever a new island is encountered.
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