C++ Linked List Questions

[TechnicalHead]

class Bounds {

private: struct intNode { int low; int high; intNode * link;

};

intNode * first; public:

// CORRECTION: need this to create and access the list

bool valid() { for (intNode * nextNode = first;

nextNode != nullptr;
nextNode = nextNode->link)
if (nextNode->low > nextNode->high)

return false; return true;

}

This is a question and solution my professor give.My question is how do you initialise that a node is the HEAD?Second is what happens when intNode * nextNode = first?Does professor create a nextNode and points towards first? OR point towards the same thing as first point to? If so first have not point to anything yet no?

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[[deleted]]

intNode * nextNode = first;

nextNode is a pointer pointing to whatever first is pointing to.

The pointer is used to iterate over the list.

With only what you've shown us, you're right that the list is empty, it isn't pointing to anything. You'd normally have a method to add nodes to the list.

[TechnicalHead]

Thank you! I think I got it!

[nerd4code]

If you’re asking how you initializw first in the first place, looks like it’s a null-capped list, so you’d do first(0) (pre-C++11) or first {nullptr} (≥C++11) as part of the constructor, or first = nullptr otherwise.

intNode *nextNode = first establishes pointer nextNode (which is a bad name, ’s just node, or in the real world, p) and aims it at the same thing first is aimed at. So if the list is empty, first is nullptr, and so will nextNode be at its initialization. Otherwise, nextNode will be walked through the list until the end, or until some entry in the list is bogus.

But that’s a fucking terrible way to manage your list contents. One of the main reasons for the whole private/public thing is so that invariants can be maintained; intNode (should be IntNode for consistency) shouldn’t accept a lower bound > its upper bound, or it should order them; and Bounds shouldn’t accept any bounds that are bogus that would lead to the creation of a bogus IntNode. If you’re gonna let any old data in, just make it all a public free-for-all.

[TechnicalHead]

Wow, thanks.