Go language single linked list deletion node: Why can't you change the linked list structure directly by modifying the pointer?

Go language single linked list deletion node: detailed explanation of pointer transfer and value modification

This article discusses the problem of pointer passing in Go single linked list deletion node operation, explains why directly modifying pointers cannot change the linked list structure, and provides the correct solution.

Problem: Direct modification of pointer is invalid

Go language function parameters adopt a value transfer mechanism. Even if the parameter is a pointer type, it is passed a copy of the pointer value, not the pointer itself. The following code snippet demonstrates this problem:

 type linklist struct {
    next *linklist
    data interface{}
}

func newnodelist(value interface{}) *linklist {
    return &linklist{data: value, next: nil}
}

func (l *linklist) delete(index int) {
    if index == 0 {
        l = l.next // Modify only local replicas}
}

func main() {
    list := newnodelist(1)
    list.delete(0) // list not modified}

The delete function tries to delete the first node of the linked list. However, l = l.next only modified the value of the local variable l inside the function, and the original linked list structure did not change. list variable in main function still points to the original head node.

Solution: Return the modified pointer

In order to correctly modify the linked list structure, the delete function needs to return the modified linked list header pointer:

 func (l *linklist) delete(index int) *linklist {
    if index == 0 {
        l = l.next
    }
    Return l
}

main function needs to reassign list variable:

 func main() {
    list := newnodelist(1)
    list = list.delete(0) // Key: reassign }

Only by returning and reassigning the value can list variable point to the updated header.

Summarize

Understanding the Go language pointer delivery mechanism and localization of function parameters is crucial to correctly writing linked list operations. Directly modifying the received copy of pointer in the function cannot change the value of the external variable. The linked list structure must be updated by returning the modified pointer and reassigning the value.

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