Golang实现数的几种遍历

目录

• PreOrder
  • recursive
  • Iterative
• InOrder
  • Iterative
• PostOrder
  • Iterative

PreOrder

recursive

package main

import "fmt"

type TreeNode struct {
	val   int
	Left  *TreeNode
	Right *TreeNode
}

func preorderTraversal(root *TreeNode) {
	if root == nil {
		return
	}
	fmt.Println(root.val)
	preorderTraversal(root.Left)
	preorderTraversal(root.Right)
}

func main() {
	/*
                            10
                           /  
                         20    30
                        /       
                      40  50     60
		      /
		     70
	*/

	root := &TreeNode{10, nil, nil}
	root.Left = &TreeNode{20, nil, nil}
	root.Right = &TreeNode{30, nil, nil}
	root.Left.Left = &TreeNode{40, nil, nil}
	root.Left.Right = &TreeNode{50, nil, nil}
	root.Right.Right = &TreeNode{60, nil, nil}
	root.Left.Left.Left = &TreeNode{70, nil, nil}

	fmt.Println("Preorder Traversal - Recursive Solution : ")
	preorderTraversal(root)
}

Iterative

package main

import "fmt"

type TreeNode struct {
	val   int
	Left  *TreeNode
	Right *TreeNode
}

func preorderTraversal(root *TreeNode) {
	if root == nil {
		return
	}
	stack := make([]*TreeNode, 0)

	for root != nil || len(stack) != 0 {
		for root != nil {
			fmt.Println(root.val)
			stack = append(stack, root)
			root = root.Left
		}
		v := stack[len(stack)-1]
		stack = stack[:len(stack)-1]
		root = v.Right
	}
}

func main() {
	/*
                            10
                           /  
                         20    30
                        /       
                      40  50     60
		      /
		     70
	*/

	root := &TreeNode{10, nil, nil}
	root.Left = &TreeNode{20, nil, nil}
	root.Right = &TreeNode{30, nil, nil}
	root.Left.Left = &TreeNode{40, nil, nil}
	root.Left.Right = &TreeNode{50, nil, nil}
	root.Right.Right = &TreeNode{60, nil, nil}
	root.Left.Left.Left = &TreeNode{70, nil, nil}

	fmt.Println("Preorder Traversal - Iterative Solution : ")
	preorderTraversal(root)
}

另一种写法

func preorderTraversal(root *TreeNode) {
	if root == nil {
		return
	}
	stack := make([]*TreeNode, 0)
	stack = append(stack, root)

	for len(stack) != 0 {
		node := stack[len(stack)-1]
		stack = stack[:len(stack)-1]
		fmt.Println(node.val)

		if node.Right != nil {
			stack = append(stack, node.Right)
		}
		if node.Left != nil {
			stack = append(stack, node.Left)
		}
	}
}

InOrder

Iterative

func inorderTraverse(root *TreeNode) {
	if root == nil {
		return
	}
	stack := make([]*TreeNode, 0)

	for root != nil || len(stack) != 0 {
		for root != nil {
			stack = append(stack, root)
			root = root.Left
		}
		node := stack[len(stack)-1]
		stack = stack[:len(stack)-1]
		fmt.Println(node.val)
		root = node.Right
	}
}

PostOrder

Iterative

func postorderTraversal(root *TreeNode) {
	if root == nil {
		return
	}
	stack := make([]*TreeNode, 0)
	var lastNode *TreeNode

	for root != nil || len(stack) != 0 {
		for root != nil {
			stack = append(stack, root)
			root = root.Left
		}
		node := stack[len(stack)-1]
		if node.Right == nil || node.Right == lastNode {
			stack = stack[:len(stack)-1]
			lastNode = node
			fmt.Println(node.val)
		} else {
			root = node.Right
		}
	}
}