Efficiently find first repeated character in a string without using any additional data structure in one traversal

Implement a space efficient algorithm to check First repeated character in a string without using any additional data structure in one traversal. Use additional data structures like count array, hash, etc is not allowed.

Examples : 

Input : abcfdeacf
Output : char = a, index= 6

The idea is to use an integer variable and uses bits in its binary representation to store whether a character is present or not. Typically an integer has at-least 32 bits and we need to store presence/absence of only 26 characters.

Implementation:

Char = a and Index = 6

Time Complexity: O(n) 
Auxiliary Space: O(1)

This article is contributed by Mr. Somesh Awasthi.