第一个只出现一次的字符

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.

样例

Given s = "lintcode", return 0.
Given s = "lovelintcode", return 2

代码实现

public class Solution {
    /**
     * @param s a string
     * @return it's index
     */
    public int firstUniqChar(String s) {
        if (s == null || s.length() == 0) {
            return -1;
        }
        //字符是一个长度为8的数据类型，因此总共有256种可能
        //每个字母根据其ASCLL码值作为数组的下标创建一个长度为256的数组
        int[] str = new int[256];
        for(char c : s.toCharArray()) {
            str[c]++;
        }
        for (int i =0; i < s.length(); i++) {
            if (str[s.charAt(i)] == 1) {
                return i;
            }
        }
        return -1;
    }
}