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godeep-copyternary-tree

How do you perform a deep copy of a ternary tree in Go?


I'm attempting to perform a deep copy of the following struct:

// Ternary Tree
type Tree struct {
    Left  *Tree
    Mid *Tree
    Right *Tree
    Value interface{}
    Parent *Tree
    Orientation string
    IsTerminal bool
    Type string
}

The following is my sorry attempt. It looks like I'm creating a new tree at the root but it's children are still pointing to the same address in memory.

func (tree *Tree) CopyTree() *Tree {
    if (tree == nil) {
        return nil
    } else {
        copiedTree := &Tree {
            tree.Left.CopyTree(),
            tree.Mid.CopyTree(),
            tree.Right.CopyTree(),
            tree.Value,
            tree.Parent.CopyTree(),
            tree.Orientation,
            tree.IsTerminal,
            tree.Type}
        return copiedTree
    }
}

Are there any useful constructs in go that assist with deep copying a struct? If not, how would I perform this deep copy myself? Note, the "deepcopy" package no longer works as it uses a few functions that were deprecated with the release of Go 1


Solution

  • I was close. I should have assigned the copiedTree to the parent property.

    func (tree *Tree) CopyTree() *Tree {
        if (tree == nil) {
            return nil
        } else {
            copiedTree := &Tree {
                tree.Left.CopyTree(),
                tree.Mid.CopyTree(),
                tree.Right.CopyTree(),
                tree.Value,
                nil,
                tree.Orientation,
                tree.IsTerminal,
                tree.Type,
            }
    
            if copiedTree.Left != nil {
                copiedTree.Left.Parent = copiedTree
            }
            if copiedTree.Right != nil {
                copiedTree.Right.Parent = copiedTree
            }
            if copiedTree.Mid != nil {
                copiedTree.Mid.Parent = copiedTree
            }
            return copiedTree
        }
    }