First Unique Character in a String

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.

找出给定小写字符串中最早出现的不重复字符

   public int firstUniqChar(String s) {
        /**
         * 只有26个字母，所以初始化一个长度26的数组
         */
        int[] freq = new int[26];
        for(int i = 0 ; i< s.length();i++){
            //循环给出的字符串字符，将其相应的数组下标元素+1
            //那么该数组中元素=1的下标就是所有不重复的字符
            freq[s.charAt(i) - 'a'] ++ ;
        }
        //找到所有不重复的字符之后，接下就是找出s中第一个出现的不重复字符
        //再次循环s字符串字符判断第一个元素=1的下标就是结果
        for(int i = 0; i< s.length();i++){
            if(freq[s.charAt(i) - 'a'] == 1){
                return i;
            }
        }
        return -1;
    }