binary-tree-concurrent-walker.go

package main

import (
	"fmt"
	"math/rand"
)

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

func (t *Tree) String() string {
	if t == nil {
		return "()"
	}
	s := ""
	if t.Left != nil {
		s += t.Left.String() + " "
	}
	s += fmt.Sprint(t.Value)
	if t.Right != nil {
		s += " " + t.Right.String()
	}
	return "(" + s + ")"
}

func insert(t *Tree, v int) *Tree {
	if t == nil {
		return &Tree{nil, v, nil}
	}
	if v < t.Value {
		t.Left = insert(t.Left, v)
	} else {
		t.Right = insert(t.Right, v)
	}
	return t
}

// New returns a new, random binary tree holding the values k, 2k, ..., 10k.
func New(k int) *Tree {
	var t *Tree
	for _, v := range rand.Perm(10) {
		t = insert(t, (1+v)*k)
	}
	return t
}

// Walk walks the tree t sending all values
// from the tree to the channel ch.
func Walk(t *Tree, ch chan int) {
	recursiveWalk(t, ch)
	close(ch)
}

func recursiveWalk(t *Tree, ch chan int) {
	if t == nil {
		return
	}
	recursiveWalk(t.Left, ch)
	ch <- t.Value
	recursiveWalk(t.Right, ch)
}

// Same determines whether the trees
// t1 and t2 contain the same values.
func Same(t1, t2 *Tree) bool {
	ch1 := make(chan int)
	ch2 := make(chan int)

	go Walk(t1, ch1)
	go Walk(t2, ch2)

	for {
		v1, ok1 := <-ch1
		v2, ok2 := <-ch2

		if ok1 != ok2 {
			return false
		}

		if v1 != v2 {
			return false
		}

		return true
	}
}

func main() {
	ch := make(chan int)
	t1 := New(1)

	go Walk(t1, ch)

	fmt.Printf("t1 values: ")
	for v := range ch {
		fmt.Printf("%d ", v)
	}

	t2 := New(2)
	fmt.Printf("\n\nis\n%s\nis equal to\n%s\n%v\n", t1, t1, Same(t1, t1))
	fmt.Printf("\nis\n%s\nis equal to\n%s\n%v\n\n", t1, t2, Same(t1, t2))

}

// t1 values: 1 2 3 4 5 6 7 8 9 10
//
// is
// ((((1 (2)) 3 (4)) 5 ((6) 7 ((8) 9))) 10)
// is equal to
// ((((1 (2)) 3 (4)) 5 ((6) 7 ((8) 9))) 10)
// true
//
// is
// ((((1 (2)) 3 (4)) 5 ((6) 7 ((8) 9))) 10)
// is equal to
// ((((2) 4 (6)) 8 (10 (12))) 14 ((16) 18 (20)))
// false