Medium

Quiz

#299 Bulls and Cows

APPROACH

In the Bulls and Cows guessing game you write down a secret number. When your friend guesses, you provide a hint with:

- The number of "bulls": digits that are correct in both value and position.

- The number of "cows": non-bull digits in the guess that appear in the secret but at the wrong position — specifically, the non-bull guess digits that could be rearranged to become bulls.

Given secret and guess, return the hint as "xAyB" where x is the bull count and y is the cow count. Both strings 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.

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What is the optimal approach for this problem?