299. Bulls and Cows

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:

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.

思路：

第一次遍历找出所有位置相同且值相同的数字，即bulls，并且记录secret中不是bulls的数字出现的次数。

然后第二次遍历我们针对guess中不是bulls的位置，如果在哈希表中存在，cows自增1，然后映射值减1

public class Solution {
 public static String getHint(String secret, String guess) {
	TreeMap<Character, Integer> map=new TreeMap<Character,Integer>();
		char[] secrectCharArray = secret.toCharArray();
		char[] guessCharArray = guess.toCharArray();
		int bullsCount = 0, cowsCount = 0;

		// bullsCount
		for (int i = 0; i < secrectCharArray.length; i++) {
			if (secrectCharArray[i] == guessCharArray[i]) {
				bullsCount++;
			}
			else
			{
				if(!map.containsKey(secrectCharArray[i]))//
					map.put(secrectCharArray[i], 1);
				else 
					map.put(secrectCharArray[i], map.get(secrectCharArray[i])+1);
			}
		}
		// cowsCount
		for (int i = 0; i < guessCharArray.length; i++) {
			if (secrectCharArray[i] == guessCharArray[i])// 非Bulls位置
			{
				continue;
			}
			else
			{
				char curChar=guessCharArray[i];
				if (map.containsKey(curChar) && map.get(curChar) > 0) {
					cowsCount++;
					map.put(curChar, map.get(curChar) - 1);
				}
			}
		}
		return String.valueOf(bullsCount) + "A" + String.valueOf(cowsCount) + "B";
	}
}