Leetcode 299:Bulls and Cows

You are playing the followingBulls and Cowsgame with your friend: You write down a number and ask your friend to guess what the number is. Each time your friend makes a guess, you provide a hint that indicates how many digits in said guess match your secret number exactly in both digit and position (called "bulls") and how many digits match the secret number but locate in the wrong position (called "cows"). Your friend will use successive guesses and hints to eventually derive the secret number.

For example:

Secret number:  "1807"
Friend's guess: "7810"

Hint:1bull and3cows. (The bull is8, the cows are0,1and7.)

Write a function to return a hint according to the secret number and friend's guess, useAto indicate the bulls andBto indicate the cows. In the above example, your function should return"1A3B".

Please note that both secret number and friend's guess may contain duplicate digits, for example:

Secret number:  "1123"
Friend's guess: "0111"

In this case, the 1st1in friend's guess is a bull, the 2nd or 3rd1is a cow, and your function should return"1A1B".

You may assume that the secret number and your friend's guess only contain digits, and their lengths are always equal.

Credits:
Special thanks to@jeantimexfor adding this problem and creating all test cases.

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//你和朋友在玩下面的猜數字游戲（BullsandCows）：你寫下一個4位數的神秘數字然後讓朋友來猜，
//你的朋友每次猜一個數字，你給一個提示，告訴他有多少個數字處在正確的位置上（稱為"bulls"公牛），
//以及有多少個數字處在錯誤的位置上（稱為"cows" 奶牛），你的朋友使用這些提示找出那個神秘數字。
class Solution {
public:
    string getHint(string secret, string guess) {
        int aCnt=0;//公牛的個數
        int bCnt=0;//奶牛的個數
        vector sVec(10,0);
        vector gVec(10,0);
        if(secret.length()!=guess.length() || secret.empty())
            return "0A0B";
        for(int i=0;i