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First Unique Character in a String

Given a string s, find the first non-repeating character and return its index. Return -1 if no such character exists.

Input:

leetcode

Output:

Reasoning:

First, we count the frequency of each character in the string s = leetcode.
Then, we iterate over the string to find the first character with a frequency of $1$ .
We find that the character l appears only once and it is the first character in the string, so its index is $0$ .
The final output is the index of the first non-repeating character, which is $0$ .

Editor

Python 3.13.1

0/0

Run code to see test results.

📘

Given a string s, find the first non-repeating character and return its index. Return -1 if no such character exists.

Input:

leetcode

Output:

Reasoning:

First, we count the frequency of each character in the string s = leetcode.
Then, we iterate over the string to find the first character with a frequency of $1$ .
We find that the character l appears only once and it is the first character in the string, so its index is $0$ .
The final output is the index of the first non-repeating character, which is $0$ .

Editor

Python 3.13.1

0/0

Run code to see test results.