Solution: Letter Combinations of a Phone Number
Explore how to use the subsets pattern and backtracking to generate all possible letter combinations from a string of phone digits. Understand the recursive approach, how to handle each digit's possible letters, and manage backtracking to build valid solutions efficiently. This lesson helps you grasp a key coding pattern for interview problems involving combinations.
We'll cover the following...
Statement
Given a string containing digits from 2 to 9 inclusive, with the possibility of each digit appearing multiple times, return all possible letter combinations that the number could represent. Return the answer in any order.
The illustration below shows the mapping of digits to letters in a telephone dial pad.
Note: The number on the telephone dial pad does not correspond to any letter, so the input string only contains digits from to .
Constraints:
-
digits.length -
digits[i]is a digit in the range
Pattern: Subsets
This problem lends itself naturally to the subsets pattern. To solve this problem, we can use a backtracking algorithm as the solution template to correctly generate all the possible combinations.
Solution
Since we need to explore different choices for each digit and generate valid combinations, we can use the subset technique with backtracking. It involves iterating through each ...