Describe a situation where storing items in an array is clearly better than stor

Question

Describe a situation where storing items in an array is clearly better than storing items on a linked list

Explanation / Answer

Arrays in C (as well as other languages) are used to store related data in one container. This container can be of any basic data type (ints, chars, etc) or any user defined data structures. The basic syntax is as follows: datatype variablename[size]; //General Example int var[10]; //Array named 'var' with 10 ints (currently not initialized) int var[] = {0,0,0,0}; //Array named 'var' with 4 ints all initialized to 0 char var[]; //Syntax error (you need to declare the size) The way to read this would be "variablename has size elements of datatypes" or "var has 10 elements of ints". Here are some basic tidbits for arrays: The size is also called the index of the array In C, index values start from 0 and go up. They can be any unsigned integer (no doubles, floats, chars, etc...). Accessing an out of bounds element is always dangerous because sometimes the compiler will throw an error and sometimes it'll just run along happily accessing garbage values. To make sure this doesn't happen always use the following loop structure [indent] int x; int array[]= { 3, 6, 9, 12, 15 }; for (x=0; x< (sizeof(array)/sizeof(int)); x++) { //Do your code } [/indent]Now finally I'll talk about arrays and the memory they're stored in. Array elements are stored in contiguous memory (for those that don't know contiguous memory just means memory thats next to each other). Lets say you declare an array as follows int array[2] = {1,3}; So you have two elements array[0] = 1 and array[1] = 3. Now lets say that the element 0 is stored in memory at location 0x700000 this means that element 1 would be stored at location 0x700004 since ints are 4 bytes. With this example you can see what I mean by contiguous memory. Linked Lists Linked lists are a series of nodes containing arbitrary data fields, linked together by pointers. Linked lists can be linked in one of two ways: 1) Singly linked or 2) Doubly linked. In both types the next node is connected by a pointer pointing to its location in memory. In the doubly linked list each node also has a pointer pointing to the location in memory of the previous node. Linked lists can become much more complex than arrays because of the need for memory management. Below is a simple structure of a node. struct node { int data; node* next; } node; As you can see each node has two fields. The first field is the data field, this could be any data type. The second field is a pointer to another node structure. This will be used as the next pointer. Here's how you would declare a new pointer. struct node* head = NULL; head = malloc(sizeof(struct node)); You'll see that I've created a pointer to a node called "head" and assigned it NULL. Now why did I assign it null instead of just leaving it blank. Well, mainly because it's good practice. When you don't assign it anything "head" would be pointing to a garbage value in memory and could cause problems. Now because of the next step it really doesn't matter but its always good practice to assign all pointers the value of NULL initially. So now that you have the node pointer "head" initialized how do I add data to it? head->data = 1; head->node = secondNode; Here secondNode is an already initialized node. Here's a sample program on making a linked list struct node { int data; node* next; } node; void main(){ struct node * curr, *head; int i; head = NULL; for(i = 1; i < 10; i++){ curr = malloc(sizeof(struct node)); cur->data = i; cur->next = head; head = cur; } curr = head; while(curr){ printf("%d ", curr->data); curr = curr->next; } } This program loops 10 times each time creating a new node (called curr) and placing it as the new head. If you wanted to place it at the tail you'd just just do the loop this way: for(i = 1; i < 10; i++){ curr = malloc(sizeof(struct node); head-> data = i; head->next = curr; head = curr; } So now that you know what arrays are and what linked lists are when should you use one another and what are their strengths and weaknesses

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