【GoLang笔记】A Tour of Go - Exercise: Equivalent Binary Trees

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本文是GoLang学习教程中的一道习题，具体题目要求及代码实现如下。

Exercise: Equivalent Binary Trees
1. Implement the Walk function.
2. Test the Walk function.

The function tree.New(k) constructs a randomly-structured 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.

一种实现如下：

package main

import "code.google.com/p/go-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) {
	//fmt.Println("tree=", t)
	left := t.Left
	right := t.Right
	if (left == nil) && (right == nil) {
		//fmt.Println("child=", t.Value)
	    ch <- t.Value
		return
	}
	
	if left != nil {
	    Walk(left, ch)
	}

	if (left != nil) || (right != nil) {
	    //fmt.Println("parent=", t.Value)
	    ch <- t.Value
	}
	
	if right != nil {
	    Walk(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)
	ch2 := make(chan int)
	go Walk(t1, ch1)
	go Walk(t2, ch2)
	
	depth := 10
	for i := 0; i < depth; i++ {
		x1 := <- ch1
		x2 := <- ch2
		if x1 != x2 {
		    return false
		}
	}
    
	return true
}

func main() {
/*
	ch1 := make(chan int)
	ch2 := make(chan int)
	go Walk(tree.New(1), ch1)
	go Walk(tree.New(2), ch2)
	
	for i := 0; i < 10; i++ {
	    fmt.Println(<-ch1)
	}
	for i := 0; i < 10; i++ {
	    fmt.Println(<-ch2)
	}
*/	
	fmt.Println(Same(tree.New(1), tree.New(2)))
}

===================== EOF ===================

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