(java)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:设置两个flag数组，flag1和flag2,，分别表示secret中的位置和guess中的位置是否被计数过。

先遍历一遍secret和guess早出相同位置上相同元素的个数。并将这些位的flag1和flag2标志为1,。然后再遍历secret和guess寻找不同位置上相同元素的个数，找到一对标志一对，防止重复计数。

代码如下(已通过leetcode)

public class Solution {

public String getHint(String secret, String guess) {

int countA=0,countB=0;

int[] flag1=new int[secret.length()];

int[] flag2=new int[secret.length()];

int i=0,j=0;

for(int k=0;k<secret.length();k++) {

if(secret.charAt(k)==guess.charAt(k)) {

countA++;

flag1[k]=1;

flag2[k]=1;

}

}

for(i=0;i<secret.length();i++) {

for(j=0;j<secret.length();j++) {

if(flag1[i]!=0) break;

else {

if(flag2[j]!=0) continue;

else {

if(secret.charAt(i)==guess.charAt(j)) {

if(i!=j) {

countB++;

flag1[i]=1;

flag2[j]=1;

}

}

}

}

}

}

return countA+"A"+countB+"B";

}

}