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

本文是GoLang學習教程中的一道習題，具體題目要求及代碼實現如下。

備註：由於天朝GFW屏蔽了GAE，所以GoLang官網及學習教程需要翻牆才能訪問。

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.

一種實現如下（深度優先中序遍歷）：

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)))
}

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