"Generate Parentheses"

Author: lennylxx

README.md

@@ -269,7 +269,7 @@ The `☢` means that you need to have a LeetCode Premium Subscription.
 | 25  | [Reverse Nodes in k-Group]                                   |                    |
 | 24  | [Swap Nodes in Pairs]                                        |                    |
 | 23  | [Merge k Sorted Lists]                                       |                    |
-| 22  | [Generate Parentheses]                                       |                    |
+| 22  | [Generate Parentheses]                                       | [C++](src/21.cpp)  |
 | 21  | [Merge Two Sorted Lists]                                     | [C](src/21.c)      |
 | 20  | [Valid Parentheses]                                          | [C](src/20.c)      |
 | 19  | [Remove Nth Node From End of List]                           | [C](src/19.c)      |

src/22.cpp

@@ -0,0 +1,43 @@
+#include <iostream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+class Solution {
+public:
+    vector<string> generateParenthesis(int n) {
+        vector<string> ans;
+        string temp = "";
+
+        generateParenthesisHelper(ans, temp, n, n);
+
+        return ans;
+    }
+
+    void generateParenthesisHelper(vector<string> &ans, string temp, int left, int right) {
+        if (left > right) return;
+
+        if (left == 0 && right == 0) {
+            ans.push_back(temp);
+            return;
+        }
+
+        if (left > 0)
+            generateParenthesisHelper(ans, temp + "(", left - 1, right);
+        if (right > 0)
+            generateParenthesisHelper(ans, temp + ")", left, right - 1);
+    }
+};
+
+int main() {
+    int n = 4;
+    Solution s;
+    vector<string> ans = s.generateParenthesis(n);
+
+    for (int i = 0; i < ans.size(); i++) {
+        cout << ans[i] << endl;
+    }
+
+    return 0;
+}