How Can We Efficiently Test for Binary Tree Equivalence in Go?

Go Equivalence Testing for Binary Trees

Binary tree equivalence testing, as seen in the Go Tour Exercise #7, poses a challenge in determining the equivalence of two trees containing the same values. One may attempt to achieve this by concurrently traversing both trees and sending their values to channels. However, ensuring the termination of the traversal and the signaling of the absence of remaining elements proves to be a crucial obstacle.

The provided code attempts to handle this task by sending values from the trees to channels and consuming them concurrently in the Same function. However, using close(ch) within the Walk function is problematic as it prematurely terminates the channel, preventing all values from being sent.

Fortunately, an elegant solution emerged from the golang-nuts group that leverages closures to address this issue:

func Walk(t *tree.Tree, ch chan int) {
    defer close(ch) // Closes the channel upon function return
    var walk func(t *tree.Tree)
    walk = func(t *tree.Tree) {
        if t == nil {
            return
        }
        walk(t.Left)
        ch <- t.Value
        walk(t.Right)
    }
    walk(t)
}

The revised code utilizes a closure to implement the tree traversal. The defer statement ensures that the channel is closed upon the completion of the traversal. This mechanism gracefully handles the signaling of the absence of remaining elements, ensuring the accurate equivalence check.

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