An Answer to A Tour of Go Exercise: Equivalent Binary Trees

exercise-equivalent-binary-trees.go

package main

import (
	"golang.org/x/tour/tree"
	"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 != nil { // if empty node, stop looking
		Walk(t.Left, ch) // otherwise, look left first
		ch <- t.Value // send the current node to the channel
		Walk(t.Right, ch) // and look right
	} // continue until all looks come up empty
}

// Same determines whether the trees
// t1 and t2 contain the same values.
func Same(t1, t2 *tree.Tree) bool {
	ch1, ch2 := make(chan int), make(chan int) // make channels
	go func() { // go to the first tree
		Walk(t1, ch1) // kick off the walker
		close(ch1) // wait to close until the walk is done
	}() // call the go
	go func() { // repeat for the second tree
		Walk(t2, ch2)
		close(ch2)
	}()
	for i := range ch1 { // iterate over one of the channels
		if i != <-ch2 { // at each step, see if nodes are the same
			return false // if not, trees are not the same
		}
	}
	return true // if no dissimilar nodes, trees are the same
}

func main() {	
	ch := make(chan int)
	go func() { // test walk a tree
		Walk(tree.New(1), ch)
		close(ch) // make sure to close when walk is done
	}()
	for i := range ch {
		fmt.Println(i)
	}
	fmt.Println(Same(tree.New(1), tree.New(1))) // should be true
	fmt.Println(Same(tree.New(1), tree.New(2))) // should be false
}