Leetcode 299. Bulls and Cows

Problem

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.

Algorithm

Use three list to record the state, if a number is used just ignore it.

Code

class Solution:
    def getHint(self, secret: str, guess: str) -> str:
        slen = len(secret)
        bulls = [0] * slen
        cows = [0] * slen
        used = [0] * slen
        for i in range(slen):
            if secret[i] == guess[i]:
                bulls[i] = 1
                used[i] = 1
        for i in range(slen):
            if not bulls[i]:
                for j in range(slen):
                    if i != j and not bulls[j] and not used[j]:
                        if secret[j] == guess[i]:
                            cows[i] = 1
                            used[j] = 1
                            break
        
        return str(sum(bulls)) + "A" + str(sum(cows)) + "B"