LC - Bulls and Cows

 

https://leetcode.com/problems/bulls-and-cows/

Examples:

Secret: 1807    　　　　　　　　　　　　　　　　　　Secret: 1123

Guess: 7810    ====> "0A3B"　　　　　　　　　　Guess:  0111      ====> "1A1B"

Secret: 1122    　　　　　　　　　　　　　　　　　　Secret: 121

Guess: 1222   ====> "3A0B"　　　　　　　　　　  Guess: 222        ====> "1A0B"

 

So getting the bull number is easy by just counting the number of matched pairs. The problem is to count the number of cows(mismatches).

1)Mismatched element from guess string has to exist in secret string.

2)The # of mimatched occurence of that element in guess = # of mimatched occurence of that element in secret ;

3)We keep track of each mismatched pair by increasing the number by 1 for secret string and decreasing the number by 1 for guess string

4)If count[guess]>0,then that means  this element has occured in secret string and it was a mismactch, thus,we can increase the cow since this element is now found in the guess string;

5)If count[secret]<0,then that means  this element has occured in guess string and it was a mismactch, thus,we can increase the cow since this element is now found in the secret string;

    public String getHint(String secret, String guess) {
        if((secret==null||secret.length()==0)||(guess==null||guess.length()==0)){
            return "0A0B";
        }
        int match=0;
        int mismatch=0;
        int[] count=new int[10];
        for(int i=0;i<secret.length();i++){
             char s=secret.charAt(i);
             char g=guess.charAt(i);
        if(s==g){
            match++;
        }else{
             if(count[s-'0']<0){
                mismatch++;
            }
            if(count[g-'0']>0){
                mismatch++;
            }
            count[g-'0']--;
            count[s-'0']++;
        }
    }
    return match+"A"+mismatch+"B";
 }