Added the solution of 'Letter Combinations of Phone Number in C++' in medium…

Medium/ word-break.cpp

@@ -1,32 +1,35 @@
-class Solution {
+class Solution
+{
 public:
-
-
-    bool solve(int i,set<string>&st , string &target,int m, vector<int>&dp) {
-
-    if(i==m) return true ;
-
-   if(dp[i] != -1) return dp[i] ; 
-
-    string temp  = "" ;
-    for(int j = i ; j<m ; j++) {
-
-        temp += target[j] ;
-        if(st.count(temp))
-              if (solve(j+1 ,st,target,m,dp)) return dp[i] = 1 ;
+    bool solve(int i, set<string> &st, string &target, int m, vector<int> &dp)
+    {
+
+        if (i == m)
+            return true;
+
+        if (dp[i] != -1)
+            return dp[i];
+
+        string temp = "";
+        for (int j = i; j < m; j++)
+        {
+
+            temp += target[j];
+            if (st.count(temp))
+                if (solve(j + 1, st, target, m, dp))
+                    return dp[i] = 1;
+        }
+        return dp[i] = 0;
     }
-       return dp[i] = 0 ;
-
-}
-
-
-    bool wordBreak(string s, vector<string>& wordDict) {
-
-    set<string>st ;
-    for(auto x : wordDict) st.insert(x) ;
-    int m = s.size() ;
-    vector<int>dp(m+1,-1) ;
-    return solve(0,st,s,m,dp) ;
-
+
+    bool wordBreak(string s, vector<string> &wordDict)
+    {
+
+        set<string> st;
+        for (auto x : wordDict)
+            st.insert(x);
+        int m = s.size();
+        vector<int> dp(m + 1, -1);
+        return solve(0, st, s, m, dp);
     }
 };

Medium/LetterCombinationsPhoneNumber.cpp

@@ -0,0 +1,39 @@
+// 17. Letter Combinations of a Phone Number
+
+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;
+    }
+};