Letter Combinations of a Phone Number LeetCode Programming Solutions | LeetCode Problem Solutions in C++, Java, & Python [💯Correct]

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In this post, you will find the solution for the  Letter Combinations of a Phone Number in C++, Java & Python-LeetCode problem. We are providing the correct and tested solutions to coding problems present on LeetCode. If you are not able to solve any problem, then you can take help from our Blog/website.

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Link for the Problem –  Letter Combinations of a Phone Number– LeetCode Problem

 Letter Combinations of a Phone Number– LeetCode Problem

Problem:

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.

A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.

Example 1:

Input: digits = "23"
Output: ["ad","ae","af","bd","be","bf","cd","ce","cf"]

Example 2:

Input: digits = ""
Output: []

Example 3:

Input: digits = "2"
Output: ["a","b","c"]

Constraints:

• 0 <= digits.length <= 4
• digits[i] is a digit in the range ['2', '9'].

Letter Combinations of a Phone Number– LeetCode Solutions

class Solution {
 public:
  vector<string> letterCombinations(string digits) {
    if (digits.empty())
      return {};

    vector<string> ans;

    dfs(digits, 0, "", ans);

    return ans;
  }

 private:
  const vector<string> digitToLetters{"",    "",    "abc",  "def", "ghi",
                                      "jkl", "mno", "pqrs", "tuv", "wxyz"};

  void dfs(const string& digits, int i, string&& path, vector<string>& ans) {
    if (i == digits.length()) {
      ans.push_back(path);
      return;
    }

    for (const char letter : digitToLetters[digits[i] - '0']) {
      path.push_back(letter);
      dfs(digits, i + 1, move(path), ans);
      path.pop_back();
    }
  }
};

class Solution {
  public List<String> letterCombinations(String digits) {
    if (digits.isEmpty())
      return new ArrayList<>();

    List<String> ans = new ArrayList<>();
    ans.add("");
    final String[] digitToLetters = {"",    "",    "abc",  "def", "ghi",
                                     "jkl", "mno", "pqrs", "tuv", "wxyz"};

    for (final char d : digits.toCharArray()) {
      List<String> temp = new ArrayList<>();
      for (final String s : ans)
        for (final char c : digitToLetters[d - '0'].toCharArray())
          temp.add(s + c);
      ans = temp;
    }

    return ans;
  }
}

class Solution:
  def letterCombinations(self, digits: str) -> List[str]:
    if not digits:
      return []

    ans = ['']
    digitToLetters = ['', '', 'abc', 'def', 'ghi',
                      'jkl', 'mno', 'pqrs', 'tuv', 'wxyz']

    for d in digits:
      temp = []
      for s in ans:
        for c in digitToLetters[ord(d) - ord('0')]:
          temp.append(s + c)
      ans = temp

    return