Added day11 solution

Author: avidLearnerInProgress

30-days-of-code-july/11.subsets.cpp

@@ -0,0 +1,17 @@
+class Solution {
+public:
+    vector<vector<int>> subsets(vector<int>& nums) {
+        vector<vector<int>> subs;
+        vector<int> sub;
+        subsets(nums, 0, sub, subs);
+        return subs;
+    }
+     void subsets(vector<int>& nums, int i, vector<int>& sub, vector<vector<int>>& subs) {
+        subs.push_back(sub);
+        for (int j = i; j < nums.size(); j++) {
+            sub.push_back(nums[j]);
+            subsets(nums, j + 1, sub, subs);
+            sub.pop_back();
+        }
+    }
+};