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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. class Solution {
  5. private: 
  6.     void solve(string output, vector<string>& ans, int index, vector<string>& mapping, const string& digits) {
  7.         // Base case: If index reaches the end of the input digits
  8.         if (index >= digits.size()) {
  9.             ans.push_back(output);
  10.             return;
  11.         }
  12.  
  13.         // Convert the current digit to an integer index
  14.         int number = digits[index] - '0';
  15.  
  16.         // Check if the index is valid (bounds check)
  17.         if (number < 0 || number >= mapping.size()) {
  18.             return;
  19.         }
  20.  
  21.         // Get the corresponding letters for the current digit
  22.         string values = mapping[number];
  23.  
  24.         // Loop through each character in the string values
  25.         for (char c : values) {
  26.             output.push_back(c);
  27.             solve(output, ans, index + 1, mapping, digits);
  28.             output.pop_back(); // Backtrack
  29.         }
  30.     }
  31.  
  32. public:
  33.     vector<string> letterCombinations(string digits) {
  34.         // Handle edge case for empty input
  35.         if (digits.empty()) {
  36.             return {};
  37.         }
  38.  
  39.         // Define the mapping of digits to their corresponding characters
  40.         vector<string> mapping = { " ", " ", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz" };
  41.  
  42.         // Variables for the recursive call
  43.         string output = "";
  44.         vector<string> ans;
  45.  
  46.         // Call the recursive solver
  47.         solve(output, ans, 0, mapping, digits);
  48.  
  49.         return ans; // Return the computed result
  50.     }
  51. };
  52.  
  53. int main() {
  54.     Solution sol;
  55.     string digits = "23";
  56.     vector<string> result = sol.letterCombinations(digits);
  57.  
  58.     // Output the result
  59.     for (const string& str : result) {
  60.         cout << str << " ";
  61.     }
  62.     cout << endl;
  63.  
  64.     return 0;
  65. }
  66.  
Success #stdin #stdout 0.01s 5284KB
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Standard input is empty
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ad ae af bd be bf cd ce cf
https://ideone.com/4uivzU
language:
C++ (gcc 8.3)
created:
11 days ago
visibility:
public

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