Merge pull request #304 from yigenshutiao/master

add 3 types traversal and test of binary tree

go/23_binarytree/binarytree.go

@@ -0,0 +1,66 @@
+package binarytree
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func preOrderTraversal(root *TreeNode) []int {
+	if root == nil {
+		return nil
+	}
+	if root.Left == nil && root.Right == nil {
+		return []int{root.Val}
+	}
+	var stack []*TreeNode
+	var res []int
+	stack = append(stack, root)
+	for len(stack) != 0 {
+		e := stack[len(stack)-1]
+		stack = stack[:len(stack)-1]
+		res = append(res, e.Val)
+		if e.Right != nil {
+			stack = append(stack, e.Right)
+		}
+		if e.Left != nil {
+			stack = append(stack, e.Left)
+		}
+	}
+	return res
+}
+
+func inOrderTraversal(root *TreeNode) []int {
+	if root == nil {
+		return nil
+	}
+	if root.Left == nil && root.Right == nil {
+		return []int{root.Val}
+	}
+	res := inOrderTraversal(root.Left)
+	res = append(res, root.Val)
+	res = append(res, inOrderTraversal(root.Right)...)
+
+	return res
+}
+
+func postOrderTraversal(root *TreeNode) []int {
+	if root == nil {
+		return nil
+	}
+	var res []int
+	if root.Left != nil {
+		lres := postOrderTraversal(root.Left)
+		if len(lres) > 0 {
+			res = append(res, lres...)
+		}
+	}
+	if root.Right != nil {
+		rres := postOrderTraversal(root.Right)
+		if len(rres) > 0 {
+			res = append(res, rres...)
+		}
+	}
+	res = append(res, root.Val)
+	return res
+}

go/23_binarytree/binarytree_test.go

@@ -0,0 +1,94 @@
+package binarytree
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var tcs = []struct {
+	pre, in, post []int
+}{
+
+	{
+		[]int{1, 2, 3},
+		[]int{1, 3, 2},
+		[]int{3, 2, 1},
+	},
+
+	{
+		[]int{1, 2, 4, 5, 3, 6, 7},
+		[]int{4, 2, 5, 1, 6, 3, 7},
+		[]int{4, 5, 2, 6, 7, 3, 1},
+	},
+	// 可以有多个 testCase
+}
+
+func PreIn2Tree(pre, in []int) *TreeNode {
+	if len(pre) != len(in) {
+		panic("preIn2Tree 中两个切片的长度不相等")
+	}
+
+	if len(in) == 0 {
+		return nil
+	}
+
+	res := &TreeNode{
+		Val: pre[0],
+	}
+
+	if len(in) == 1 {
+		return res
+	}
+
+	idx := indexOf(res.Val, in)
+
+	res.Left = PreIn2Tree(pre[1:idx+1], in[:idx])
+	res.Right = PreIn2Tree(pre[idx+1:], in[idx+1:])
+
+	return res
+}
+
+func indexOf(val int, nums []int) int {
+	for i, v := range nums {
+		if v == val {
+			return i
+		}
+	}
+
+	return 0
+}
+
+func Test_preOrderTraversal(t *testing.T) {
+	ast := assert.New(t)
+
+	for _, tc := range tcs {
+		fmt.Printf("~~%v~~\n", tc)
+
+		root := PreIn2Tree(tc.pre, tc.in)
+		ast.Equal(tc.pre, preOrderTraversal(root), "输入:%v", tc)
+	}
+}
+
+func Test_inOrderTraversal(t *testing.T) {
+	ast := assert.New(t)
+
+	for _, tc := range tcs {
+		fmt.Printf("~~%v~~\n", tc)
+
+		root := PreIn2Tree(tc.pre, tc.in)
+		ast.Equal(tc.in, inOrderTraversal(root), "输入:%v", tc)
+	}
+}
+
+func Test_postOrderTraversal(t *testing.T) {
+	ast := assert.New(t)
+
+	for _, tc := range tcs {
+		fmt.Printf("~~%v~~\n", tc)
+
+		root := PreIn2Tree(tc.pre, tc.in)
+		ast.Equal(tc.post, postOrderTraversal(root), "输入:%v", tc)
+	}
+}