[Function add]

1. Add c++ version of leetcode solutions.

Author: Seanforfun

Diff for: leetcode/40. Combination Sum II.md

@@ -123,3 +123,35 @@ class Solution {
     }
 }
 ```
+
+### C++ version
+* Method 1: Recursion
+	```objectivec
+	class Solution {
+		int target_;
+		
+		void recursion(vector<int>& candidates, int index, int sum, vector<int>& cur, vector<vector<int>>& res_){
+			if(target_ == sum) res_.push_back(cur);
+			else if(sum < target_){
+				int size = candidates.size();
+				for(int i = index; i < size; ++i){
+					while(i > index && i < size && candidates[i] == candidates[i - 1]) ++i;
+					if(i >= size) break;
+					cur.emplace_back(candidates[i]);
+					recursion(candidates, i + 1, sum + candidates[i], cur, res_);
+					cur.pop_back();
+				}
+			}
+		}
+	public:
+		vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
+			if(candidates.empty()) return {};
+			sort(candidates.begin(), candidates.end());
+			vector<vector<int>> res_;   
+			vector<int> cur;
+			target_ = target;
+			recursion(candidates, 0, 0, cur, res_);
+			return res_;
+		}
+	};
+	```

Diff for: leetcode/77. Combinations.md

@@ -89,3 +89,28 @@ class Solution {
     }
 }
 ```
+
+### C++ Version
+* Method 1: Recursion
+	```objectivec
+	class Solution {
+		void recursion(int n, int cur, int k, vector<int>& temp, vector<vector<int>>& res){
+			if(k == temp.size()) res.emplace_back(temp);
+			else{
+				for(int i = cur; i <= n; ++i){
+					temp.emplace_back(i);
+					recursion(n, i + 1, k, temp, res);
+					temp.pop_back();
+				}
+			}
+		}
+	public:
+		vector<vector<int>> combine(int n, int k) {
+			if(k == 0 || n < k) return {};
+			vector<vector<int>> res;
+			vector<int> cur;
+			recursion(n, 1, k, cur, res);
+			return res;
+		}
+	};
+	```

Diff for: leetcode/78. Subsets.md

@@ -102,3 +102,26 @@ class Solution {
     }
 }
 ```
+
+### C++ version
+* Method 1: power set
+	```objectivec
+	class Solution {
+		vector<vector<int>> res;
+		void dfs(int cur, vector<int>& nums, vector<int>& temp){
+			res.emplace_back(temp);
+			for(int i = cur; i < nums.size(); ++i){
+				temp.emplace_back(nums[i]);
+				dfs(i + 1, nums, temp);
+				temp.pop_back();
+			}
+		}
+	public:
+		vector<vector<int>> subsets(vector<int>& nums) {
+			if(nums.empty()) return {};
+			vector<int> temp;
+			dfs(0, nums, temp);
+			return res;
+		}
+	};
+	```

Diff for: leetcode/90. Subsets II.md

@@ -125,4 +125,29 @@ class Solution {
         }
     }
 }
+```
+
+### C++ version
+```objectivec
+class Solution {
+    vector<vector<int>> res_;
+    void dfs(int cur, vector<int>& temp, vector<int>& nums){
+        res_.emplace_back(temp);
+        int size = nums.size();
+        for(int i = cur; i < size; ++i){
+            while(i > cur && i < size && nums[i] == nums[i - 1]) ++i;
+            if(i >= size) break;
+            temp.emplace_back(nums[i]);
+            dfs(i + 1, temp, nums);
+            temp.pop_back();
+        }
+    }
+public:
+    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
+        sort(nums.begin(), nums.end());
+        vector<int> temp;
+        dfs(0, temp, nums);
+        return res_;
+    }
+};
 ```