387. First Unique Character in a String

Description

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.

s = "loveleetcode",
return 2.
Note: You may assume the string contain only lowercase letters.

Solution

HashTable

class Solution {
    public int firstUniqChar(String s) {
        char[] count = new char[26];
        
        for (int i = 0; i < s.length(); ++i) {
            ++count[s.charAt(i) - 'a'];
        }
        
        for (int i = 0; i < s.length(); ++i) {
            if (count[s.charAt(i) - 'a'] == 1) {
                return i;
            }
        }
        
        return -1;
    }
}