如何比较两个通用链表? [英] How can two generic linked list in swift can be compared?

问题描述

我有一个通用链表，如果每个节点值相同且顺序正确，我可以检查两个链表是否相等. 我有一个将链接列表分为两部分的函数，稍后我要检查两个列表在其节点中是否具有相同的值.

I have a generic linked list and I can check if two linked list are equal if each of the node value are same and are in order. I have a function which divides linked list in two part and later I want to check two list has same value in it's node.

func divideList(atIndex index:Int) -> (first: LLGeneric<T>?,second: LLGeneric<T>?)

我正在寻找用例，可以在分割并比较后(在反转一个列表之后)检查链接列表中的回文.

I looking it for my use case where I can check palindrome in linked list after dividing and then comparing ( after reversing one list).

注意:我的链表节点是通用的

Note: my linked list node is generic something like

   class LLGenericNode<T> {
    var value: T
    var next: LLGenericNode?
    weak var previous: LLGenericNode?
    init(_ value: T) {
        self.value = value
    }
}

推荐答案

为了比较值，您必须要求T为Equatable:

In order to compare values you have to require that T is Equatable:

class LLGenericNode<T: Equatable> {
    // ...
}

然后您可以通过首先比较值来实现==. 如果值相等，则对列表尾部进行递归比较.

Then you can implement == by comparing the values first. If the values are equal, the list tails are compared recursively.

extension LLGenericNode: Equatable {
    static func ==(lhs: LLGenericNode<T>, rhs: LLGenericNode<T>) -> Bool {
        if lhs.value != rhs.value {
            return false
        }
        switch (lhs.next, rhs.next) {
        case (nil, nil):
            // Both tails are == nil:
            return true
        case let (lvalue?, rvalue?):
            // Both tails are != nil:
            return lvalue == rvalue // Recursive call
        default:
            // One tails is nil and the other isn't:
            return false
        }
    }
}

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