First Unique Character in a String

387. First Unique Character in a String

Difficulty: Easy

Related Topics: Hash Table, String, Queue, Counting

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

Code:

class Solution:
    def firstUniqChar(self, s: str) -> int:
        chardict = {}
        for i in s:
            if i in chardict:
                chardict[i]=-1
            else:
                chardict[i]=s.index(i)
        for i in chardict:
            if chardict[i] != -1:
                return chardict[i]
        return -1

Feedbacks:

I made a dictionary to store keys and values. If key is laready in the dictionary, I make the value of that key to -1. So after traversing through the whole string, I return the first value that is not -1. If all of the values are -1, I return -1.