Find First Unique Character in a String

You are given a string S of length N. Your task is to find the index (considering 1-based indexing) of the first unique character in the string. If there are no unique characters, return -1.

Example:

Input:

T = 2 N = 5 S = "hello" N = 4 S = "aabb"

Output:

1 -1

Explanation:

The first unique character in "hello" is 'h', which is at index 1. The string "aabb" has no unique characters.

Constraints:

1 ≤ T ≤ 100

1 ≤ N ≤ 10^4

Note:

A unique character in a string is one that appears only once.

Question

Find First Unique Character in a String

You are given a string S of length N. Your task is to find the index (considering 1-based indexing) of the first unique character in the string. If there are no unique characters, return -1.

Example:

Input:

 T = 2 
 N = 5 
 S = "hello" 
 N = 4 
 S = "aabb"

Output:

 1 
 -1

Explanation:

The first unique character in "hello" is 'h', which is at index 1. The string "aabb" has no unique characters.

Constraints:

1 ≤ T ≤ 100
1 ≤ N ≤ 10^4

Note:

A unique character in a string is one that appears only once.

Accepted Answer

Find the index of the first unique character in a given string, return -1 if no unique characters are found.

Iterate through the string to count the frequency of each character
Iterate through the string again to find the first character with frequency 1
Return the index of the first unique character or -1 if none found