Algorithms

A handy collection of C algorithms compiled into one header file for use anywhere. Feel free to include this file with any C project, as long as you keep the comment at the top with a little copyright notice.

Table of Contents

1. Stacks
2. Queues
3. Linked Lists
4. Heap(Priority Queue)

Stack

Functions

//Creates new stack.
void new();
//Frees stack memory.
void free(Stack *s);
//Pushes item to top of the stack.
void push(item, Stack *s);
//Removes item on top of the stack and returns it.
item pop(Stack *s);
//Prints stack size, memory usage.
void print(Stack s);
//Returns 1 if empty stack, 0 otherwise.
int is_empty(Stack s);

Description

The stack is probably the most basic storage structure, using the 'first-in, first-out' approach. To define a stack, the user must first know what type the stack is, either a primitive type, or a struct. To define a stack, you must first define the STACK_TYPE to int, float, char, or whatever type you wish. Then, include the handystack header file.

#define STACK_TYPE int 
#include "handystack.h" 

To define more than one stack, STACK_TYPE must first be undefined. #undef STACK_TYPE Then you simply define the type, and include the header again. Do not try to define two of the same type, however, as that will give all sorts of nasty errors.

Example

The following example creates a stack of doubles, pushes 45.000 onto it, and prints the stack's characteristics.

#define STACK_TYPE double
#include "handystack.h"
double_stack myStack = new_double_stack();
push_double_stack(45.000, &myStack);
print_double_stack(myStack);

Notice that the function names are characteristic of the STACK_TYPE you've defined earlier? The functions have the following basic format: FUNCTION_ + STACK_TYPE + _stack Where FUNCTION is the name of the function.

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Queue

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Linked List

Functions

//Creates a new list.
list* new(data, next);
//Recursively frees a list.
void free(List *l);
//Returns the number of elements in a list.
int size(List *l);
//Returns a new list with an item added to the front.
List* add(data, List *l);
//Returns a new list with an item inserted at an index.
List* insert(data, index, List *l);
//Returns the item at an index.
data get(index, List *l);
//Returns a new list with an item at an index removed.
List* remove(index, List *l);

Description

The linked list is a list where each node is comprised of a piece of data and a pointer to the next node. The list can have items added, inserted, and removed. To define a list, first define the type of data the list will contain, and then include the handylist header file.

#define LIST_TYPE float
#include "handylist.h"

To define multiple lists, you must first undefine LIST_TYPE like so. #undef LIST_TYPE Then you simply repeat the instructions above for whatever new list type you would like to make. Just be sure to not define two list types for the same type.

Example

The following example creates a list of char and adds a few to the list, and prints the number added.

#define LIST_TYPE char
#include "handylist.h"
char_list* myList = new_char_list('a', NULL);
myList = add_char_list('b', myList);
myList = add_char_list('c', myList);
myList = insert_char_list('g', 1, myList);
printf("List size: %d\n", size_char_list(myList));

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Heap (Priority Queue)

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