Search⌘ K
AI Features
Home
Courses
Grokking the Coding Interview Patterns in Python

Solution: Bulls and Cows

Explore how to implement a single-pass hash map solution to the Bulls and Cows problem. Understand how to count bulls—digits in the correct position—and cows—digits matching but misplaced—while optimizing time and space complexity. This lesson helps you apply hash maps effectively in interview problems related to matching and counting characters.

We'll cover the following...

Statement

You are playing a number guessing game called “Bulls and Cows” with a friend.

You write down a secret number, and your friend tries to guess it. After each guess, you provide a hint based on the following:

  • Bulls: The number of digits that are in the correct position in the guess.

  • Cows: The number of digits that are in both the secret and the guess but in different positions. (These are non-bull digits that could become bulls if rearranged.)

Your task is to return a hint for the guess, formatted as “xAyB”, where:

  • x is the number of bulls.

  • y is the number of cows.

Note: Both the secret number and the guess may contain duplicate digits.

Constraints:

  • 1<=1 <= secret.length, guess.length ...