Mastercard Interview Questions

Given a string, find the first non-repeating character in it and return its index. If it doesn’t exist, return -1.

Example questions:

Consider a string where all characters are lowercase alphabets.

Example 1:

Input:

s = 'helloworld'

Output:

first_uniq_char(s) -> 0

In the string ‘helloworld’, the first non-repeating character is ‘h’, which is at index 0.

Example 2:

Input:

s = 'concussion'

Output:

first_uniq_char(s) -> 4

In the string ‘concussion’, the first non-repeating character is ‘u’, which is at index 4.