Java Coding Practice

Solve Phone Keypad Letter Combinations using Java Language

Solve Phone Keypad Letter Combinations using Java to enhance your skills with java coding practice , master coding concepts, and prepare for interviews with practical exercises and detailed solutions.

Phone Keypad Letter Combinations

Difficulty : Easy

Categories :

  • Backtracking

Given a string s containing only digits (0-9), find all possible letter combinations that the number could represent on a phone keypad (like old mobile phones). The mapping is:

  • 2 -> 'abc'
  • 3 -> 'def'
  • 4 -> 'ghi'
  • 5 -> 'jkl'
  • 6 -> 'mno'
  • 7 -> 'pqrs'
  • 8 -> 'tuv'
  • 9 -> 'wxyz'

Return all possible combinations in lexicographical order.

Constraints:

  • 0 ≤ s.length ≤ 4
  • s contains only digits from 2-9

Examples:

Input: s = "23"
Output: ["ad","ae","af","bd","be","bf","cd","ce","cf"]
Explanation: All combinations of letters for '2' (abc) and '3' (def)
Input: s = "5"
Output: ["j","k","l"]
Explanation: All possible letters for '5'

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Arrays A collection of elements stored in contiguous memory locations, allowing efficient random access and manipulation.

Linked Lists A linear data structure where each element (node) points to the next, offering dynamic memory allocation and efficient insertions/deletions.

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Dynamic Programming An optimization technique that solves problems by breaking them into overlapping subproblems and storing their results.

Backtracking A problem-solving method that explores all possibilities recursively, backtracking when a solution is not feasible.

Sorting Algorithms Techniques for arranging elements in a specific order, such as quicksort, mergesort, and bubble sort, essential for data organization.

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