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Quick Summary

Generate all valid letter combinations from a digit string using a custom phone keypad mapping.
Consecutive identical digits can be grouped, where the group size selects the corresponding letter from the mapping.
Systematically explore all valid groupings and letter selections using recursion.

What This Tests

Recursive backtracking and decision tree exploration
String partitioning and dynamic index tracking
Constraint validation during state transitions
Combinatorial generation techniques

Common Patterns

Backtracking

Accepted

1.6k/3k

Acceptance Rate52.6%

Test Cases

Input

digits =

Output

Expected