Round 1:

It was a coding test held on the CoCubes platform. Three problems were given with varying marks:

2 marks: Given a string, find the first non-repeating character in it. For example, if the input string is “GeeksforGeeks”, the output should be ‘f’; if the input string is “GeeksQuiz”, the output should be ‘G’.

This question was easy to solve, requiring just a simple implementation using a HashMap.

3 marks: Given a number in string format, find the next palindrome larger than the number.

5 marks: Given a singly linked list L0 -> L1 -> … -> Ln-1 -> Ln. Rearrange the nodes in the list so that the new list is: L0 -> Ln -> L1 -> Ln-1 -> L2 -> Ln-2 …

Round 2 (Fly Round):

This was a pen-and-paper round. We needed to solve the given problems on paper using both brute-force and optimized approaches.

Q1. Given an array A[] of n numbers and another number x, determine whether or not there exist two elements in the array whose sum is exactly x.

Q2. The problem was to count all possible paths from the top-left to the bottom-right of an m x n matrix, with the constraint that from each cell, you can only move right or down.

Tips to crack this round:

1. Write legibly. Good handwriting matters to some extent.
2. Write the approach first and comment your code well.
3. Finally, write the time and space complexity of the solution. All these matter to an extent.

Twelve students were selected for the next round.

Swap two numbers without using a third variable or arithmetic operators. It was a cakewalk. This can be done using the bitwise XOR operator.