Stuck on "Bulls and Cows"

Puzzles
#1

In the classic code-breaking game of Bulls and Cows, your opponent chooses a 4-digit secret number, and you need to guess it. After each guess, your opponent tells you how many “bulls” and how many “cows” are in your guess, interpreted as:

  • Each bull indicates a digit in your guess that exactly matches the value and position of a digit in your opponent’s secret number.

  • Each cow indicates a digit in your guess that matches the value of a digit in your opponent’s secret number, but is in the wrong position.

So for example, if the secret number is 1234 and you guess 5678, your guess has 0 bulls and 0 cows. However, if you guess 2324 then your guess has 1 bull (the 4) and 2 cows (one of the 2s, and the 3.)

You will be given a series of guesses along with the number of bulls and cows in each guess. Your job is to determine the secret number based on the given information.

NOTE: This version of the game deviates from the classic Bulls and Cows rules in that digits may be repeated any number of times in the secret number.

#2

It will be easier to help you if you tell us what you understood, what you tried, etc.

General tips for this problem:
Bulls should be easy to count, just zip/compare.
Also, it’s easier to count both bulls/cows together than cows alone.
And then you substract bulls to get cows alone.

Write few examples and try to find a way to count bulls/cows together with basic observations.

1 Like
#3

This is my approach:- I can find no of bulls & cows. But i am not able to figure out how to get the secret number

class Solution {
	public String getHint(String secret, String guess) {
		int[] map = new int[10];
		int n = secret.length();
		int bulls =0, cows =0;
		for(char c : secret.toCharArray()){
			map[c-'0']++;
		}
		for(char c : guess.toCharArray()){
			if(map[c-'0']-- >0)
				cows++;
		}

		for(int i=0; i<n; i++){
			if(secret.charAt(i) == guess.charAt(i))
				bulls++;
		}

		return String.valueOf(bulls)+"A"+String.valueOf(cows-bulls)+"B";
	}
}
#4

Ok so now all you have to do is to check all strings from 0000 to 9999 and find the one that matches all the bulls/cows given.