From 68eca139ca107d17d0fbc56f906699b7d2b82258 Mon Sep 17 00:00:00 2001
From: Jason Staten <code@jxs.me>
Date: Sun, 16 Oct 2022 20:19:54 -0600
Subject: [PATCH] genparen

---
 genparen/genparen.go      | 25 +++++++++++++++++++++++++
 genparen/genparen_test.go | 24 ++++++++++++++++++++++++
 genparen/readme.md        | 24 ++++++++++++++++++++++++
 3 files changed, 73 insertions(+)
 create mode 100644 genparen/genparen.go
 create mode 100644 genparen/genparen_test.go
 create mode 100644 genparen/readme.md

diff --git a/genparen/genparen.go b/genparen/genparen.go
new file mode 100644
index 0000000..7352a5f
--- /dev/null
+++ b/genparen/genparen.go
@@ -0,0 +1,25 @@
+package genparen
+
+func iter(result *[]string, current string, left int, right int) {
+	if left == 0 && right == 0 {
+		*result = append(*result, current)
+		return
+	}
+
+	if left > 0 {
+		iter(result, current+"(", left-1, right)
+	}
+	if right > left {
+		iter(result, current+")", left, right-1)
+	}
+}
+
+func generateParenthesis(n int) []string {
+	result := make([]string, 0, n^2)
+	iter(&result, "", n, n)
+	return result
+}
+
+func Gen(n int) []string {
+	return generateParenthesis(n)
+}
diff --git a/genparen/genparen_test.go b/genparen/genparen_test.go
new file mode 100644
index 0000000..8cc94df
--- /dev/null
+++ b/genparen/genparen_test.go
@@ -0,0 +1,24 @@
+package genparen_test
+
+import (
+	"testing"
+
+	"git.jxs.me/leetgo/genparen"
+	"github.com/stretchr/testify/require"
+)
+
+func TestEmpty(t *testing.T) {
+	require.Equal(t, []string{""}, genparen.Gen(0))
+}
+
+func TestOne(t *testing.T) {
+	require.Equal(t, []string{"()"}, genparen.Gen(1))
+}
+
+func TestTwo(t *testing.T) {
+	require.Equal(t, []string{"(())", "()()"}, genparen.Gen(2))
+}
+
+func TestThree(t *testing.T) {
+	require.Equal(t, []string{"((()))", "(()())", "(())()", "()(())", "()()()"}, genparen.Gen(3))
+}
diff --git a/genparen/readme.md b/genparen/readme.md
new file mode 100644
index 0000000..79fa50e
--- /dev/null
+++ b/genparen/readme.md
@@ -0,0 +1,24 @@
+22. Generate Parentheses
+Medium
+
+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
+
+