题解 | #第一个只出现一次的字符#

public class Solution {
    public int FirstNotRepeatingChar(String str) {
        if(str == null || str.length() == 0){
            return -1;
        }

        char[] arr = str.toCharArray();
        int[] cnt = new int['z' - 'A' + 1];
        int[] pos = new int['z' - 'A' + 1];

        for(int i = 0; i < arr.length; ++i){
            pos[arr[i] - 'A'] = i;
            cnt[arr[i] - 'A']++;
        }

        for(int i = 0; i < arr.length; ++i){
            if(cnt[arr[i] - 'A'] == 1){
                return pos[arr[i] - 'A'];
            }
        }

        return -1;
    }
}