Game of Master Mind - Cracking the coding interview--Q19.5

Cracking the coding interview--Q19.5
The Game of Master Mind is played as follows:
The computer has four slots containing balls that are red (R ), yellow (Y), green (G) or blue (B). For example, the computer might have RGGB (e.g., Slot #1 is red, Slots #2 and #3 are green, Slot #4 is blue).
You, the user, are trying to guess the solution. You might, for example, guess YRGB.When you guess the correct color for the correct slot, you get a "hit". If you guess a color that exists but is in the wrong slot, you get a "pseudo-hit". For example, the guess YRGB has 2 hits and one pseudo hit.
For each guess, you are told the number of hits and pseudo-hits. Write a method that, given a guess and a solution, returns the number of hits and pseudo hits.
译文：
Master Mind游戏规则如下：
4个槽，里面放4个球，球的颜色有4种，红(R )，黄(Y)，绿(G)，蓝(B)。比如， 给出一个排列RGGB，表示第一个槽放红色球，第二和第三个槽放绿色球，第四个槽放蓝色球。
你要去猜这个排列。比如你可能猜排列是：YRGB。当你猜的颜色是正确的，位置也是正确的， 你就得到一个hit，比如上面第3和第4个槽猜的和真实排列一样(都是GB)，所以得到2个hit。 如果你猜的颜色在真实排列中是存在的，但位置没猜对，你就得到一个pseudo-hit。比如， 上面的R，猜对了颜色，但位置没对，得到一个pseudo-hit。
对于你的每次猜测，你会得到两个数：hits和pseudo-hits。写一个函数， 输入一个真实排列和一个猜测，返回hits和pseudo-hits。

这个问题十分直观，但有一个地方需要去向面试官明确一下题意。关于pseudo-hits的定义， 猜对颜色但位置没对，得到一个pseudo-hit，这里是否可以包含重复？举个例子， 比如真实排列是：RYGB，猜测是：YRRR。那么hits很明显为0了。pseudo-hits呢？ 猜测中Y对应真实排列中的Y，得到一个pseudo-hits。猜测中有3个R， 而真实排列中只有一个，那这里应该认为得到1个pseudo-hits还是3个？ CTCI书认为是3个，想必理由是猜测中的3个R都满足：出现在真实排列中，位置不正确。 所以算3个。但我认为，这里算1个比较合理，真实排列中的R只和猜测中的一个R配对， 剩余的没有配对，不算。弄清题意后，代码就不难写出了。

http://www.bozhiyue.com/yuyan/2016/0614/190284.html

 public static class Result {
        public int hits;
        public int pseudoHits;
        
        public Result(int h, int p) {
            hits = h;
            pseudoHits = p;
        }
        
        public Result() {
        }
        
        public String toString() {
            return "(" + hits + ", " + pseudoHits + ")";
        }
 };

 public static int code(char c) {
        switch (c) {
        case 'B':
                return 0;
        case 'G':
                return 1;
        case 'R':
                return 2;
        case 'Y':
                return 3;
        default:
                return -1;
        }
 }

 public static int MAX_COLORS = 4;

 public static Result estimate(String guess, String solution) {
        if (guess.length() != solution.length()) return null;
        Result res = new Result();
        int[] frequencies = new int[MAX_COLORS];
            
        /* Compute hits and built frequency table */
        for (int i = 0; i < guess.length(); i++) {
            if (guess.charAt(i) == solution.charAt(i)) {
                res.hits++;
            } else {
                /* Only increment the frequency table (which will be used for pseudo-hits) if
                 * it's not a hit. If it's a hit, the slot has already been "used." */
                int code = code(solution.charAt(i));
                if (code >= 0) {
                 frequencies[code]++;  // 把答案的分布存在frequencies数组中
                }
            }
        }
        
        /* Compute pseudo-hits */
        for (int i = 0; i < guess.length(); i++) {
            int code = code(guess.charAt(i));
            if (code >= 0 && frequencies[code] > 0 && guess.charAt(i) != solution.charAt(i)) {
                res.pseudoHits++;
                frequencies[code]--;
            }
        }
        return res;
 }

https://jixiangsanbao.wordpress.com/2014/08/25/moderate-question-5/

	private static int code(char c){ switch (c){
	case 'R':
	return 0;
	case 'Y':
	return 1;
	case 'G':
	return 2;
	case 'B':
	return 3;
	default:
	return -1;
	}
	}
	public static Result countHits(char[] guess, char[] solution) throws Exception{
	if(guess.length != MAX_COLORS || solution.length != MAX_COLORS){
	throw new Exception("input has error");
	}
	int[] frequencyTable = new int[MAX_COLORS];
	Result res = new Result();
	//count hits
	for(int i = 0; i < MAX_COLORS; i++){
	if(guess[i] == solution[i]){
	res.realHits++;
	}
	else{
	int code = code(solution[i]);
	if(code >= 0){
	frequencyTable[code]++;
	}
	}
	}
	//count pseudo hits
	for(int i = 0; i < MAX_COLORS; i++){
	//if the char is not a previous hit or previous pseudo hit
	int code = code(guess[i]);
	if(code >= 0 && guess[i] != solution[i] && frequencyTable[code] > 0){
	res.pseudoHits++;
	frequencyTable[code]--;
	}
	}
	return res;
	}

https://github.com/mirandaio/interview-questions/blob/master/moderate/MasterMind.java

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