Add combination_sum.cpp (medium level problem)

C++/combination_sum.cpp

@@ -0,0 +1,44 @@
+//PROBLEM-LINK=https://leetcode.com/problems/combination-sum/
+// Runtime: 4ms
+// Memory Usage: 10 MB
+class Solution
+{
+public:
+    void cSum(vector<int> &candidates, int target, vector<int> &current, int sum, int index, vector<vector<int>> &result)
+    {
+
+        if (sum == target)
+        {
+            vector<int> temp(current.begin(), current.end());
+            sort(temp.begin(), temp.end());
+            if (count(result.begin(), result.end(), temp) == 0)
+                result.push_back(temp);
+            return;
+        }
+
+        if (sum > target)
+        {
+            return;
+        }
+
+        for (int i = index; i < candidates.size(); i++)
+        {
+            current.push_back(candidates[i]);
+            cSum(candidates, target, current, sum + candidates[i], i, result);
+            current.pop_back();
+        }
+
+        return;
+    }
+
+    vector<vector<int>> combinationSum(vector<int> &candidates, int target)
+    {
+
+        vector<vector<int>> result;
+        vector<int> current;
+
+        cSum(candidates, target, current, 0, 0, result);
+
+        return result;
+    }
+};