[Function add]

1. Add leetcode solutions in C++ version.

Author: Seanforfun

leetcode/216. Combination Sum III.md

@@ -101,3 +101,28 @@ class Solution {
     }
 }
 ```
+
+### C++ version
+* Method 1:recursion
+	```objectivec
+	class Solution {
+		vector<vector<int>> res_;
+		void dfs(vector<int>& temp, int target, int index, int sum, int k){
+			if(temp.size() == k && sum == target){
+				res_.emplace_back(temp);
+			}else if(sum < target && temp.size() < k){
+				for(int i = index; i <= 9; ++i){
+					temp.emplace_back(i);
+					dfs(temp, target, i + 1, sum + i, k);
+					temp.pop_back();
+				}
+			}
+		}
+	public:
+		vector<vector<int>> combinationSum3(int k, int n) {
+			vector<int> temp;
+			dfs(temp, n, 1, 0, k);
+			return res_;
+		}
+	};
+	```

leetcode/46. Permutations.md

@@ -98,3 +98,28 @@ class Solution {
     }
 }
 ```
+
+### C++ Version
+* Method 1:
+	```objectivec
+	class Solution {
+		vector<vector<int>> res_;
+		void dfs(int begin, int size, vector<int>& nums){
+			if(begin >= size){
+				res_.push_back(nums);
+				return;
+			}else{
+				for(int i = begin; i < size; ++i){
+					swap(nums[begin], nums[i]);
+					dfs(begin + 1, size, nums);
+					swap(nums[begin], nums[i]);
+				}
+			}
+		}
+	public:
+		vector<vector<int>> permute(vector<int>& nums) {
+			dfs(0, nums.size(), nums);
+			return res_;
+		}
+	};
+	```

leetcode/47. Permutations II.md

@@ -76,4 +76,35 @@ class Solution {
         }
     }
 }
+```
+
+### C++ version
+* Method 1:
+```objectivec
+class Solution {
+    vector<vector<int>> res_;
+    void dfs(int index, vector<bool>& visited, vector<int>& temp, vector<int>& nums){
+        if(temp.size() == nums.size()) res_.emplace_back(temp);
+        else{
+            int size = nums.size();
+            for(int i = 0; i < size; ++i){
+                if (i > 0 && nums[i] == nums[i - 1] && !visited[i - 1]) continue;
+                if(visited[i]) continue;
+                visited[i] = true;
+                temp.emplace_back(nums[i]);
+                dfs(i + 1, visited, temp, nums);
+                temp.pop_back();
+                visited[i] = false;
+            }
+        }
+    }
+public:
+    vector<vector<int>> permuteUnique(vector<int>& nums) {
+        vector<bool> visited(nums.size(), false);
+        vector<int> temp;
+        sort(nums.begin(), nums.end());
+        dfs(0, visited, temp, nums);
+        return res_;
+    }
+};
 ```

leetcode/784. Letter Case Permutation.md

@@ -57,3 +57,26 @@ Note:
     }
     ```
 
+### C++ version
+* Method 1:
+	```objectivec
+	class Solution {
+		vector<string> res_;
+		void dfs(string s, int index, string temp){
+			if(index == s.length()) res_.emplace_back(temp);
+			else{
+				if(!isalpha(s[index])){
+					dfs(s, index + 1, temp + s[index]);
+				}else{
+					dfs(s, index + 1, temp + (char)tolower(s[index]));
+					dfs(s, index + 1, temp + (char)toupper(s[index]));
+				}
+			}
+		}
+	public:
+		vector<string> letterCasePermutation(string S) {
+			dfs(S, 0, "");
+			return res_;
+		}
+	};
+	```