Java [Leetcode 387]First Unique Character in a String

题目描述：

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.

解题思路：

开个26个数的数组，然后先对字符串过一遍，统计每个字母出现的次数，然后从头再国一遍，第一个字母数为1的即为首先出现并且只出现一次的字母。

代码如下：

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