First unique character in a string

Moderate

0/80

Average time to solve is 15m

6 upvotes

Asked in companies

Problem statement

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 present in the string. If there are no unique characters return -1.

Note

A unique character in a string is the character that appears only once in the string. For example, ‘h’, ‘e’, and ‘o’ are the unique characters in the string “hello”.

Detailed explanation ( Input/output format, Notes, Images )

Input format :

The first line of input contains a single integer T, denoting the number of test cases.

The first line of each test case contains a positive integer N, which represents the length of the string.

The next line of each test case contains a string S.

Output Format :

For each test case, return the index of the first unique character, and if there is no unique character return “-1”.

Note:

You do not need to print anything. It has already been taken care of. Just implement the given function.

Constraint :

1 <= T <= 100
1 <= N <= 10^4

Time Limit: 1 sec

Sample Input 1 :

2
16
codingninjascode
24
practicepracticepractice

Sample Output 1:

6
-1

Explanation for Input 1:

For the first subtask the explanation is given in the problem statement. 

For the second subtask there are no unique characters so ans is -1.

Sample Input 2 :

3
19
palindromemordnilap
9
notunique
7
caaabbc

Sample Output 2:

10
2
-1

Explanation for Input 2:

For the first subtask, every character except ‘e’ occurs 2 times so we print the index of e that is 10. 

For the second subtask, the characters ‘o’ , ‘t’ , ‘e’ , ‘i’ and ‘q’ are unique but ‘o’ occurs before all the other unique characters .

For the third subtask, all the characters are not unique so we return -1.

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