Hi!! I am having some issues creating this linked list. I am receiving errors specifically about memory leaks. I have written a few parts already in the LinkedList.h. I still need the following:Head(), Tail(), GetNode, Operator[](), Find, FindAll, the copy constructor, the copy assignment operator, InsertBefore(), InsertAfter(), InsertAt(), operator==, RemoveHead(), RemoveTail(), RemoveAt(), Remove(), Clear(), PrintForwardRecursive, PrintReverseRecursive.
In addition to the my issue with the memory leak
COP3503 Programming Fundamentals 2 Project 1 – Templated Linked List Overview The purpose of this assignment is for you to write a data structure called a Linked List, which utilizes templates (similar to Java’s generics), in order to store any type of data. In addition, the nature of a Linked List will give you some experience dealing with non-contiguous memory organization. This will also give you more experience using pointers and memory management. Pointers, memory allocation, and understand how data is stored in memory will serve you well in a variety of situations, not just for an assignment like this. Background Remember Memory? Variables, functions, pointers—everything takes up SOME space in memory. Sometimes that memory is occupied for only a short duration (a temporary variable in a function), sometimes that memory is allocated at the start of a program and hangs around for the lifetime of that program. Visualizing memory can be difficult sometimes, but very helpful. You may see diagrams of memory like this: Or, you may see diagrams like these: If you are trying to draw out some representation of memory to help you solve a problem, any of these (or some alternative that makes sense to you) will be fine. x y Car r g b a Other Memory int x, y, z; Vehicle car; char r, g, b, a; Vehicle *ptr = &car; z ptr 0x665418b0 0x665418b4 0x665418b8 0x665418bc 0x665418c0 0x665418c4 0x665418c8 0x665418cc 0x665418d0 x y z Car r int x, y, z; int x, y, z; COP3503 Programming Fundamentals 2 Arrays Arrays are stored in what is called contiguous memory. A contiguous memory block is one that is not interrupted by anything else (i.e. any other memory block). So if you created an array of 5 integers, each of those integers would be located one after the other in memory, with nothing else occupying memory between them. This is true for all arrays, of any data type. All of the data in an application is not guaranteed to be contiguous, nor does it need to be. Arrays are typically the simplest and fastest way to store data, but they have a grand total of zero features. You allocate one contiguous block, but you can’t resize it, removing elements is a pain (and slow), etc. Consider the previous array. What if you wanted to add another element to that block of memory? If the surrounding memory is occupied, you can’t simply overwrite that with your new data element and expect good results. In this scenario, in order to store one more element you would have to: 1. Create another array that was large enough to store all of the old elements plus the new one 2. Copy over all of the data elements one at a time (including the new element, at the end) 3. Free up the old array—no point in having two copies of the data This process has to be repeated each time you want to add to the array (either at the end, or insert in the middle), or remove anything from the array. It can be quite costly, in terms of performance, to delete/rebuild an entire array every time you want to make a single change. Cue the Linked List! 2 4 6 8 10 Other Memory Other Memory someArray int someArray[5]; someArray[0] = 2; someArray[1] = 4; someArray[2] = 6; someArray[3] = 8; someArray[4] = 10; 2 4 6 8 10 Someone else’s memory Other Memory someArray[5] = 12; // #badIdea This will almost certainly break. Old Array 2 4 6 8 10 Someone else’s memory Other Memory -- -- -- -- -- -- Create New Array Uninitialized values 2 4 6 8 10 Someone else’s memory Other Memory 2 4 … … … 12 Copy old data to the new array And the “new guy” Someone else’s memory Other Memory 2 4 6 8 10 12 Newly available memory Lastly, delete the old array COP3503 Programming Fundamentals 2 Linked List The basic concept behind a Linked List is simple: 1. It’s a container that stores its elements in a non-contiguous fashion 2. Each element knows about the location of the element which comes after it (and possibly before, more on that later) So instead of a contiguous array, where element 4 comes after element 3, which comes after element 2, etc… you might have something like this: Each element in the Linked List (typically referred to as a “node”) stores some data, plus some sort of reference (a pointer, in C++) to whatever node should come next. The First node knows only about itself, and the Second node. The Second node knows only about itself, and the Third, etc. In this example the Fourth node has a null pointer as its “next” node, indicating that we’ve reached the end of the data. A real-world example can be helpful as well: Think about a line of people, with one person at the front of the line. That person might know about the person who is next in line, but no further than that (beyond him or herself, the person at the front doesn’t need to know or care). The second person in line might know about the third person in line, but no further. Continuing on this way, the last person in line knows that there is no one else that follows, so that must be the end. So… What are the advantages of storing data like this? When inserting or removing elements into an array, the entire array has to be reallocated. With a Linked List, only a small number of elements are affected. Only elements surrounding the changed element need to be updated, and all other elements can remain unaffected. This makes the Linked List much more efficient when it comes to adding or removing elements. Now, imagine one person wants to step out of line. If this were an array, all of the data would have to be reconstructed elsewhere. In a Linked List, only three nodes are affected: 1) The person leaving, 2) the person in front of that person, and 3) the person behind that person. Imagine you are the person at the front of the line. You don’t really need to know or care what happens 10 people behind you, as that has no impact on you whatsoever. … First … Second Third Fourth … Null First in line etc… Next == null, must be at the end COP3503 Programming Fundamentals 2 If the 5th person in line leaves, the only parts of the line that should be impacted are the 4th, 5th, and 6th spaces. 1. Person 4 has a new “next” Person: whomever was behind the person behind them (Person 6). 2. Person 5 has to be removed from the list. 3. Person 6… actually does nothing. In this example, a Person only cares about whomever comes after them. Since Person 5 was before Person 6, Person 6 is unaffected. (A Linked List could be implemented with two-way information between nodes—more on that later). The same thought-process can be applied if someone stepped into line (maybe a friend was holding their place): In this case, Person 2 would change their “next” person from Person 3, to the new Person being added. New Guy would have his “next” pointer set to whomever Person 2 was previously keeping track of, Person 3. Because of the ordering process, Person 3 would remain unchanged, as would anyone else in the list (aside from being a bit irritated at the New Guy for cutting in line). So that’s the concept behind a Linked List. A series of “nodes” which are connected via pointer to one another, and inserting/deleting nodes is a faster process than deleting and reconstructing the entire collection of data. Now, how to go about creating that? Terminology Node The fundamental building block of a Linked List. A node contains the data actually being stored in the list, as well as 1 or more pointers to other nodes. This is typically implemented as a nested class (see below). Singly-linked A Linked List would be singly-linked if each node only has a single pointer to another node, typically a “next” pointer. This only allows for uni-directional traversal of the data—from beginning to end. Doubly-linked Each node contains 2 pointers: a “next” pointer and a “previous” pointer. This allows for bi-directional traversal of the data—either from front-to-back or back- to-front. Head A pointer to the first node in the list, akin to index 0 of an array. Tail A pointer to the last node in the list. May or may not be used, depending on the implementation of the list. First Leaver First New Guy COP3503 Programming Fundamentals 2 Nested Classes The purpose of writing a class is to group data and functionality. The purpose of a nested class is the same—the only difference is where we declare a nested class. We declare a nested class like this: class MyClass { public: // Nested class struct NestedClass { int x, y, z; int SomeFunction(); }; private: // Data for "MyClass" NestedClass myData[5]; NestedClass *somePtr; float values[10]; // Etc… }; // To create nested classes… // Use the Scope Resolution Operator MyClass::NestedClass someVariable; // With a class template… TemplateClass
foo; TemplateClass::Nested bar; /* NOTE 1: You can make nested classes private if you wish, to prevent access to them outside of the encapsulating class. */ /* Why is NestedClass a struct in this case? No reason in particular. Remember a struct is just a class with public access by default. */ /* NOTE 2: Nested classes and templates can make for some ugly code. Be sure to read the section at the end about typename */ Additional reading: http://en.cppreference.com/w/cpp/language/nested_types The nature of the Linked