[Solved] Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Question

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Example 1:

Input: s = "leetcode"
Output: 0

Example 2:

Input: s = "loveleetcode"
Output: 2

Example 3:

Input: s = "aabb"
Output: -1

Constraints:

• 1 <= s.length <= 105
• s consists of only lowercase English letters.

Python Solution

class Solution:
    def firstUniqChar(self, s: str) -> int:
        d={}
        for i in s:
            if i not in d:
                d[i]=1
            else:
                d[i]+=1

        for k,v in d.items():
            if v==1:
                return s.index(k)
        return -1