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Microsoft
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Quick Summary
Given four digits, determine how many unique valid 24-hour times can be formed using each digit exactly once.
A valid time requires the first two digits to represent an hour between 00 and 23, and the last two to represent minutes between 00 and 59.
The fixed input size allows for exhaustive permutation checking with simple boundary validation.
What This Tests
Permutation generation and backtracking fundamentals
Constraint validation and boundary checking
Handling duplicate values and ensuring unique results
Algorithmic efficiency on fixed-size inputs
Common Patterns
Backtracking
DFS/BFS
Hashing
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