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.

Credits:

Special thanks to @jeantimex for adding this problem and creating all test cases.

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用HashMap做，没啥说的，第一次把正确的找出来，然后把猜的里面不对的字母和数量用个Map存起来，再去正解里面找一圈就好

public class Solution {
public String getHint(String secret, String guess) {
char [] s = secret.toCharArray();
char [] g = guess.toCharArray();
HashMap<Character,Integer> maps = new HashMap<>();
List<Character> postDealList = new LinkedList<>();

int A = 0,B = 0;
for(int i =0;i<s.length;i++)
{if(s[i]==g[i])A++;
else{
if(!maps.containsKey(s[i]))maps.put(s[i],0);
maps.replace(s[i],maps.get(s[i])+1);
postDealList.add(g[i]);
}

}
int size = postDealList.size();
for(int i = 0;i<size;i++){
char gu = postDealList.get(i);
if(maps.containsKey(gu)){
int val = maps.get(gu);
B++;
if(val-1==0)maps.remove(gu);
else{
maps.replace(gu,val-1);
}
}
}
return String.valueOf(A)+"A"+String.valueOf(B)+"B";
}
}