leetcode-299-Bulls-and-Cows

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描述

You are playing the following Bulls and Cows game 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: 

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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: 

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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.

分析

题目描述已经很清楚，算是细节题，先求 bull 的值，记录 guess 中的字符没在 secret 出现的次数，根据这个值再确定 cows 的值。

解决方案1(C++)

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class Solution {
public:
    string getHint(string secret, string guess) {
        int bull = 0;
        int cow = 0;
        int num[10] = {0};
        
        for(int i = 0; i < guess.size(); i++) {
            if(guess[i] == secret[i]) {
                bull++;
            }else {
                num[guess[i]-'0']++;
            }
        }
        
        for(int j = 0; j < secret.size(); j++) {
            if(guess[j] != secret[j] && num[secret[j]-'0'] > 0) {
                cow++;
                num[secret[j]-'0']--;
            }
        }
        char buff[20];
        sprintf(buff, "%dA%dB", bull, cow);
        return buff;
    }
};

解决方案2（Golang）

和 C++ 的解决方案一样。

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func getHint(secret string, guess string) string {
    bull, cow := 0, 0
    mapGuess := make([]int, 10)
    
    for i := range secret {
        if secret[i] == guess[i] {
            bull++
        } else {
            mapGuess[guess[i]-'0']++
        }
    }
    
    for i := 0; i < len(secret); i++ {
        if secret[i] != guess[i] && mapGuess[secret[i]-'0']> 0 {
            cow++
            mapGuess[secret[i]-'0']--
        }
    }
    return strconv.Itoa(bull) + "A" + strconv.Itoa(cow) + "B"
}

题目来源