leetcode 299. Bulls and Cows

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本文介绍了一种猜数字游戏的算法实现，通过计算猜测数字与秘密数字之间的公牛（正确位置与数字）和奶牛（错误位置但正确数字）的数量来提供提示。文章详细解释了如何使用Java编程语言编写一个函数，该函数接受秘密数字和猜测数字作为输入，并返回包含公牛和奶牛数量的字符串。

题目

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: 1 bull and 3 cows. (The bull is 8, the cows are 0, 1 and 7.)
Write a function to return a hint according to the secret number and friend’s guess, use A to indicate the bulls and B to 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 1st 1 in friend’s guess is a bull, the 2nd or 3rd 1 is 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.

解

public class Solution {
   public String getHint(String secret, String guess) {
        int countOfBull=0;
        int countOfCows=0;      
        int len=secret.length();

        ArrayList<Character> sL=new ArrayList<Character>();
        ArrayList<Character> gL=new ArrayList<Character>();   

        for(int i=0;i<len;i++){
            if(secret.charAt(i)==guess.charAt(i)){
                countOfBull++;
            }else{
                sL.add(secret.charAt(i));
                gL.add(guess.charAt(i));
            }
        }

       for(int i=0;i<gL.size();i++){
           if(sL.contains(gL.get(i))){
               countOfCows++;
               sL.remove(gL.get(i));
           }
       }

       return countOfBull+"A"+countOfCows+"B";


    }
}