First Unique Character in a String

题目

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.

答案

class Solution {
    public int firstUniqChar(String s) {
        int[] freq = new int[256];
        for(int i = 0; i < s.length(); i++) freq[s.charAt(i)]++;                
        for(int i = 0; i < s.length(); i++) if(freq[s.charAt(i)] == 1) return i;
        return -1;
    }
}