Create solution.cpp

Day-19/q3-Letter Combinations of a Phone Number/solution.cpp

@@ -0,0 +1,31 @@
+class Solution {
+public:
+    void generate(string &digits, int i,string &t, vector<string>&ans, vector<vector<char>>&m){
+        if(i==digits.size()){
+            ans.push_back(t);
+            return;
+        }
+        for(int j=0;j<m[digits[i]-'2'].size();j++){
+            t+=m[digits[i]-'2'][j];
+            generate(digits,i+1,t,ans,m);
+            t.pop_back();
+        }
+    }
+    vector<string> letterCombinations(string digits) {
+        vector<string>ans;
+        int n=digits.size();
+        if(n==0)return ans;
+        vector<vector<char>>m;
+        m.push_back({'a','b','c'});
+        m.push_back({'d','e','f'});
+        m.push_back({'g','h','i'});
+        m.push_back({'j','k','l'});
+        m.push_back({'m','n','o'});
+        m.push_back({'p','q','r','s'});
+        m.push_back({'t','u','v'});
+        m.push_back({'w','x','y','z'});
+        string t="";
+        generate(digits,0,t,ans,m);
+        return ans;
+    }
+};