公牛母牛问题

public class Solution {    public String getHint(String secret, String guess) {        int bulls = 0;        int cows = 0;        int[] nums = new int[10];        int len = secret.length();        for (int i = 0; i < len; i++) {            if (secret.charAt(i) == guess.charAt(i)) {                bulls++;            } else {                if (nums[secret.charAt(i) - '0']++ < 0)                    cows++;                if (nums[guess.charAt(i) - '0']-- > 0)                    cows++;            }        }        return bulls + "A" + cows + "B";    }    public static void main(String[] args) {        String secret = "1807";        String guess = "7810";        System.out.println(new Solution().getHint(secret, guess));    }}

[leetcode原题] https://leetcode.com/problems/bulls-and-cows
[参考资料] https://leetcode.com/discuss/67031/one-pass-java-solution