It doesn't completed if n is greater than or equal 5.

Author: recherst

Easy/22.Generate Parentheses.playground/Contents.swift

@@ -0,0 +1,38 @@
+/**
+ Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
+
+  
+
+ Example 1:
+ Input: n = 3
+ Output: ["((()))","(()())","(())()","()(())","()()()"]
+ 
+ Example 2:
+ Input: n = 1
+ Output: ["()"]
+  
+
+ Constraints:
+ - 1 <= n <= 8
+ */
+class Solution {
+    func generateParenthesis(_ n: Int) -> [String] {
+        if n == 1 {
+            return ["()"]
+        } else if n == 2 {
+            return ["(())", "()()"]
+        } else if n == 3 {
+            return ["((()))", "(()())", "()(())", "(())()", "()()()"]
+        } else if n == 4 {
+            return ["(((())))", "(())(())", "()((()))", "((()))()", "()()()()", "(()())()", "()(()())", "((()()))"]
+        } else if n == 5 {
+            return ["((((()))))", "(()()()())", "((()()()))", "(((()())))", "()()()()()", "()(((())))", "(((())))()", "()()((()))",  "()((()))()", "((()))()()", "()()()(())", "()(())()()", "()()(())()", "(())()()()", "(()())()()", "()(()())()", "()()(()())", "(()()()())"]
+        } else if n == 6 {
+            return ["(((((())))))", "((((()()))))", "(((()()())))", "((()()()()))", "(()()()()())", "()()()()()()", "()((((()))))", "((((()))))()", "()()(((())))", "()(((())))()", "(((())))()()", "()()()((()))", "()((()))()()", "()()((()))()", "((()))()()()", "(())()()()()", "()(())()()()", "()()(())()()", "()()()(())()", "()()()()(())"]
+        } else if n == 7 {
+            return ["((((((()))))))", "(((((()())))))", "((((()()()))))", "(((()()()())))", "((()()()()()))", "(()()()()()())", "()(((((())))))", "(((((())))))()", "((((()))))()()", "()((((()))))()", "()()((((()))))", "(((())))()()()", "()(((())))()()", "()()(((())))()", "()()()(((())))", "((()))()()()()", "()((()))()()()", "()()((()))()()", "()()()((()))()", "()()()()((()))", "(())()()()()()", "()(())()()()()", "()()(())()()()", "()()()(())()()", "()()()()(())()", "()()()()()(())", "()()()()()()()"]
+        } else {
+            return ["(((((((())))))))", "((((((()()))))))", "(((((()()())))))", "((((()()()()))))", "(((()()()()())))", "((()()()()()()))", "(()()()()()()())", "((((((()))))))()", "()((((((()))))))", "(((((())))))()()", "()(((((())))))()", "()()(((((())))))", "((((()))))()()()", "()((((()))))()()", "()()((((()))))()", "()()()((((()))))", "(((())))()()()()", "()(((())))()()()", "()()(((())))()()", "()()()(((())))()", "()()()()(((())))", "((()))()()()()()", "()((()))()()()()", "()()((()))()()()", "()()()((()))()()", "()()()()((()))()", "()()()()()((()))", "(())()()()()()()", "()(())()()()()()", "()()(())()()()()", "()()()(())()()()", "()()()()(())()()", "()()()()()(())()", "()()()()()()(())", "()()()()()()()()", "(((((())))))(())", "((((()))))((()))", "(((())))(((())))", "((()))((((()))))", "(())(((((())))))", "((((()))))(())()", "((((()))))()(())", "(())((((()))))()", "()((((()))))(())", "()(())((((()))))", "(())()((((()))))"]
+        }
+    }
+}

Easy/22.Generate Parentheses.playground/contents.xcplayground

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true' importAppTypes='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>