add the solution for leetcode 022

Author: swiftwind0405

README.md

@@ -390,7 +390,7 @@ LeetCode
 |25|[Reverse Nodes in k-Group](https://leetcode.com/problems/reverse-nodes-in-k-group/)| |Hard|
 |24|[Swap Nodes in Pairs](https://leetcode.com/problems/swap-nodes-in-pairs/)| |Medium|
 |23|[Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)| |Hard|
-|22|[Generate Parentheses](https://leetcode.com/problems/generate-parentheses/)| |Medium|
+|22|[Generate Parentheses](https://leetcode.com/problems/generate-parentheses/)| [js](./algorithms/generateParentheses/generateParentheses.js) |Medium|
 |21|[Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/)| |Easy|
 |20|[Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)| |Easy|
 |19|[Remove Nth Node From End of List](https://leetcode.com/problems/remove-nth-node-from-end-of-list/)| |Easy|

algorithms/generateParentheses/generateParentheses.js

@@ -0,0 +1,27 @@
+/**
+ * @param {number} n
+ * @return {string[]}
+ */
+var generateParenthesis = function(n) {
+    const arr = [];
+    function generate(left, right, str) {
+        // 递归终结条件：n 都用完了
+        if (left === n && right ===n) {
+            arr.push(str);
+            return;
+        }
+
+        // 如果左括号没用完（第一肯定先使用左括号），就继续递归
+        if(left < n) {
+            generate(left + 1, right, str + '(');
+        }
+
+        // 如果右括号没用完（右括号肯定比左括号少，且有括号没用完），就继续递归
+        if(right < left) {
+            generate(left, right + 1, str + ')')
+        }
+    }
+
+    generate(0, 0, '');
+    return arr;
+};