Go语言学习笔记-A Tour of Go 练习笔记-Equivalent Binary Trees

Equivalent Binary Trees

练习题目:

A function to check whether two binary trees store the same sequence is quite complex in most languages. We'll use Go's concurrency and channels to write a simple solution.

This example uses the tree package, which defines the type:

type Tree struct {
    Left  *Tree
    Value int
    Right *Tree
}

1. Implement the Walk function.

2. Test the Walk function.

The function tree.New(k) constructs a randomly-structured (but always sorted) binary tree holding the values k, 2k, 3k, ..., 10k.

Create a new channel ch and kick off the walker:

go Walk(tree.New(1), ch)

Then read and print 10 values from the channel. It should be the numbers 1, 2, 3, ..., 10.

3. Implement the Same function using Walk to determine whether t1 and t2 store the same values.

4. Test the Same function.

Same(tree.New(1), tree.New(1)) should return true, and Same(tree.New(1), tree.New(2)) should return false.

练习程序

package main

import "golang.org/x/tour/tree"
import (
	"fmt"
)

// Walk walks the tree t sending all values
// from the tree to the channel ch.
func Walk(t *tree.Tree, ch chan int){
    if t.Left != nil {
	    Walk(t.Left, ch)
	}
	ch <- t.Value
	if t.Right != nil {
	    Walk(t.Right, ch)
	}
	
}

// Same determines whether the trees
// t1 and t2 contain the same values.
func Same(t1, t2 *tree.Tree) bool {
    ch1 := make(chan int, 10)
    ch2 := make(chan int, 10)
    go Walk(t1, ch1)
    go Walk(t2, ch2)
	for i := 0; i < 10; i++ {
	   ch1_value := <-ch1
	   ch2_value := <-ch2
	   if ch1_value != ch2_value {
	       return false
	   } 
	}
	return true
}

func main() {
    t1 := tree.New(1)
    t2 := tree.New(2)
    result1 := Same(t1, t1)
    result2 := Same(t1, t2)
    fmt.Println("result is:", result1, result2)
}

运行结果：

result is: true false

学习笔记：

本题重点考察对于go语言中channels和goroutines的应用，通过使用两个goroutines Walk来实现遍历二叉树，将二叉树的节点值写入两个channels,最后进行输出对比判断是否一致。