Algorithm

Create a map that links each digit to its respective set of letters.
Prepare an empty list to hold all possible letter combinations.
Define a recursive helper function with three parameters: current index, current combination string, and the result list.
Check the base case : if the index reaches the end of the input digit string, add the current combination to the results.
For the digit at the current index, loop through all its mapped letters.
For each letter, call the helper function again with the next index and the updated combination string.

Code

#include<bits/stdc++.h>
using namespace std;

class Solution {
private:
    // Recursive function to generate letter combinations
    void func(int ind, string digits, string s, vector<string> &ans, string combos[]) {
        // Base case: if index reaches the end of digits
        if(ind == digits.size()) {
            // Add the current combination to the answer
            ans.push_back(s);
            return;
        }
        // Convert the current character to an integer
        int digit = digits[ind] - '0';
        // Loop through the corresponding characters
        for(int i = 0; i < combos[digit].size(); i++) {
            // Re