## DEV Community

Abhishek Chaudhary

Posted on

# Bulls and Cows

You are playing the Bulls and Cows game with your friend.

You write down a secret number and ask your friend to guess what the number is. When your friend makes a guess, you provide a hint with the following info:

• The number of "bulls", which are digits in the guess that are in the correct position.
• The number of "cows", which are digits in the guess that are in your secret number but are located in the wrong position. Specifically, the non-bull digits in the guess that could be rearranged such that they become bulls.

Given the secret number `secret` and your friend's guess `guess`, return the hint for your friend's guess.

The hint should be formatted as `"xAyB"`, where `x` is the number of bulls and `y` is the number of cows. Note that both `secret` and `guess` may contain duplicate digits.

Example 1:

Input: secret = "1807", guess = "7810"
Output: "1A3B"
Explanation: Bulls are connected with a '|' and cows are underlined:
"1807"
|
"7810"

Example 2:

Input: secret = "1123", guess = "0111"
Output: "1A1B"
Explanation: Bulls are connected with a '|' and cows are underlined:
"1123" "1123"
| or |
"0111" "0111"
Note that only one of the two unmatched 1s is counted as a cow since the non-bull digits can only be rearranged to allow one 1 to be a bull.

Constraints:

• `1 <= secret.length, guess.length <= 1000`
• `secret.length == guess.length`
• `secret` and `guess` consist of digits only.

SOLUTION:

``````class Solution:
def getHint(self, secret: str, guess: str) -> str:
n = len(secret)
unused = {}
bulls = 0
cows = 0
for i in range(n):
if secret[i] == guess[i]:
bulls += 1
else:
unused[secret[i]] = unused.get(secret[i], 0) + 1
for i in range(n):
if secret[i] != guess[i]:
if guess[i] in unused:
cows += 1
unused[guess[i]] -= 1
if unused[guess[i]] == 0:
del unused[guess[i]]
return "{}A{}B".format(bulls, cows)
``````