# Letter Combinations of a Phone Number

Category

Backtracking

Checkbox

Checkbox

Difficulty

Medium

Index

57

Key Ideas

The key idea to solve the "Letter Combinations of a Phone Number" problem is to use backtracking to generate all possible combinations of letters from a given phone number.

Problem Number

17

Problem Summary

**Problem Summary:**The "Letter Combinations of a Phone Number" problem asks for all possible letter combinations that can be formed by mapping digits from a phone number to letters. For example, given the input "23", the output should be a list of all possible combinations of letters that can be formed using the letters associated with the digits 2 and 3 on a phone keypad.

**Key Pitfalls:**One key pitfall to watch out for is to properly handle edge cases, such as when the input digits are empty. Another pitfall is to ensure efficient backtracking by using data structures like a hashmap or an array to store the mapping of digits to letters, rather than iterating through the digits for each combination. Lastly, it's important to handle the mapping of digits to letters correctly, as different phone keyboards may have variations in their letter assignments.

Solution Summary

The best solution for the Letter Combinations of a Phone Number problem involves backtracking. It starts by creating a mapping of each digit to its corresponding letters on a phone keypad. Then, a recursive function is used to generate all possible combinations of letters by iterating through the digits of the given phone number. At each step, the function appends a letter from the current digit's mapping to the current combination and recursively calls itself with the remaining digits. This process continues until all digits have been processed, resulting in a list of all possible letter combinations. Finally, the generated combinations are returned as the output.

Tags

Hash Table

String

Backtracking