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.

Create a hashmap to store the frequency of each character in the string.
Iterate through the string and find the first character with frequency 1.
Return the index of the first unique character or -1 if no unique characters are found.