Merge pull request #5 from akshaysoni10/LeetCode-Solution

Akshay's Leetcode solution is added

Author: kishanrajput23

Letter_Combinations_of_a_Phone_Number.cpp

@@ -0,0 +1,32 @@
+class Solution {
+private:
+    void solve(string digit, string output, int index, vector<string>& ans, string mapping[]){
+        //base case
+        if(index >= digit.length()){
+            ans.push_back(output);
+            return;
+        }
+        
+        int number = digit[index] - '0';
+        string value = mapping[number];
+        
+        for(int i=0; i<value.length(); i++){
+            output.push_back(value[i]);
+            solve(digit, output, index+1, ans, mapping);
+            output.pop_back();
+        }
+    }
+    
+public:
+    vector<string> letterCombinations(string digits) {
+        vector<string> ans;
+        if(digits.length()==0){
+            return ans;
+        }
+        string output = "";
+        int index = 0;
+        string mapping[10] = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
+        solve(digits, output, index, ans, mapping);
+        return ans;
+    }
+};