go - BST golang搜索功能

Question

您能帮忙搜索功能吗，它总是返回nil，我不明白为什么

func BTreeSearchItem(root *TreeNode, elem string) *TreeNode {
    if root == nil {
        return nil
    }
    if root.Data < elem {
        return BTreeSearchItem(root.Left, elem)
    } else if root.Data > elem {
        return BTreeSearchItem(root.Right, elem)
    }
    return root
}

试图这样做，但它返回4而不是7

func BTreeSearchItem(root *TreeNode, elem string) *TreeNode {
    if root == nil {
        return nil
    }
    if root.Data < elem {
        BTreeSearchItem(root.Left, elem)
    } else if root.Data > elem {
        BTreeSearchItem(root.Right, elem)
    }
    return root
}

完整的代码是

package main

import "fmt"

type TreeNode struct {
    Left, Right, Parent *TreeNode
    Data                string
}

func BTreeSearchItem(root *TreeNode, elem string) *TreeNode {
    if root == nil {
        return nil
    }
    if root.Data < elem {
        BTreeSearchItem(root.Left, elem)
    } else if root.Data > elem {
        BTreeSearchItem(root.Right, elem)
    }
    return root
}

func BTreeInsertData(root *TreeNode, data string) *TreeNode {
    if root == nil {
        return &TreeNode{Data: data}
    }
    if root.Data == data {
        return nil
    }
    if root.Data > data {
        if root.Left == nil {
            root.Left = &TreeNode{Data: data}
        }
        return BTreeInsertData(root.Left, data)
    }
    if root.Data < data {
        if root.Right == nil {
            root.Right = &TreeNode{Data: data}
        }
        return BTreeInsertData(root.Right, data)
    }
    return root
}

func main() {
    root := &TreeNode{Data: "4"}
    BTreeInsertData(root, "1")
    BTreeInsertData(root, "7")
    BTreeInsertData(root, "5")
    selected := BTreeSearchItem(root, "7")
    fmt.Print("Item selected -> ")
    if selected != nil {
        fmt.Println(selected.Data)
    } else {
        fmt.Println("nil")
    }

    fmt.Print("Parent of selected item -> ")
    if selected.Parent != nil {
        fmt.Println(selected.Parent.Data)
    } else {
        fmt.Println("nil")
    }

    fmt.Print("Left child of selected item -> ")
    if selected.Left != nil {
        fmt.Println(selected.Left.Data)
    } else {
        fmt.Println("nil")
    }

    fmt.Print("Right child of selected item -> ")
    if selected.Right != nil {
        fmt.Println(selected.Right.Data)
    } else {
        fmt.Println("nil")
    }
}

在互联网上搜索并通过方法发现了很多东西，但是我需要作为func。我是编程的新手，所以我很难理解

PlayGoundLink

Answer 1

我的建议是在调用函数root之前检查main()中BTreeSearchItem的值。我怀疑root值在该阶段本身已经是nil了。