add leetcode 22

Author: lijinglin3

leetcode/0022.generate-parentheses/generate_parentheses.go

@@ -0,0 +1,23 @@
+package leetcode
+
+var output []string
+
+func generateParenthesis(n int) []string {
+	output = make([]string, 0)
+	iteration(0, 0, n, "")
+	return output
+}
+
+func iteration(left int, right int, max int, s string) {
+	if left == right && left == max {
+		output = append(output, s)
+		return
+	}
+
+	if left < max {
+		iteration(left+1, right, max, s+"(")
+	}
+	if right < left {
+		iteration(left, right+1, max, s+")")
+	}
+}

leetcode/0022.generate-parentheses/generate_parentheses_test.go

@@ -0,0 +1,12 @@
+package leetcode
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGenerateParenthesis(t *testing.T) {
+	assert.Equal(t, []string{""}, generateParenthesis(0))
+	assert.Equal(t, []string{"((()))", "(()())", "(())()", "()(())", "()()()"}, generateParenthesis(3))
+}