[编程题]第一个只出现一次的字符

O(n)极简内存版

public class Solution {
    public int FirstNotRepeatingChar(String str) {
        int[] counts = new int[58];
        for(int i = 0; i < str.length(); i++)
            counts[str.charAt(i)-'A'] +=1;
        for(int i = 0; i < str.length(); i++)
            if(counts[str.charAt(i)-'A'] == 1)
                return i;
        return -1;
    }
}