320. Bulls and Cows
Medium
Frequency Reconciliation
Hashing
Problem
You are given two equal-length digit strings secret and guess. A bull is a digit that matches in both value and position. A cow is a non-bull digit from guess that exists elsewhere in secret. Return the hint in the form xAyB, where x is the number of bulls and y is the number of cows.
Examples
Example 1
Input: "1807", "7810"
Output: "1A3B"
Example 2
Input: "1123", "0111"
Output: "1A1B"
Example 3
Input: "1", "0"
Output: "0A0B"
Constraints
� 1 <= secret.length == guess.length <= 1000
� secret and guess consist only of digits.
Hints
?? Count exact-position matches as bulls immediately.
?? Only unmatched digits can become cows.
?? Frequency counts for the unmatched digits avoid double counting.
Expected Complexity
Time: O(n)
Space: O(1)
Follow-up
Can you count bulls and cows in one pass using a fixed array of size 10?
Practice Notes
Attempts: 0
Time spent: 0min
Hints used: 0
JavaScript
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Case 1
Case 2
Case 3
Input
"1807", "7810"Expected
"1A3B"