SingleLinkedList.c

#include <stdio.h>
#include <stdlib.h>

typedef struct ListNode // list node structure
{
	int value;
	struct ListNode * next;
} node_t;

node_t * newList(unsigned int size, int node_values[]) // craete a new linked list
{
	node_t * current_node, * new_node, * list_head;
	// create head
	current_node = malloc(sizeof(node_t));
	current_node->value = node_values[0];
	current_node->next = NULL;
	list_head = current_node;
	// assign more values
	for (int i = 1; i < size; ++i)
	{
		new_node = malloc(sizeof(node_t));
		new_node->value = node_values[i];
		new_node->next = NULL;
		current_node->next = new_node;
		current_node = new_node;
	}

	return list_head;
}

int listLength(node_t * list_head) // find length of the list
{
	unsigned int list_length = 1;
	node_t * current_node;
	current_node = list_head;

	while (current_node->next != NULL) // go through every item in the list
	{
		current_node = current_node->next;
		list_length++;
	}

	return list_length;
}

int getNodeValue(node_t * list_head, unsigned int node_location) // get the value of an item in a specific node
{
	if (node_location < listLength(list_head)) // check if item exists
	{
		node_t * current_node;
		current_node = list_head;

		for (int i = 0; i < node_location; ++i) // go to the position
		{
			current_node = current_node->next;
		}

		return current_node->value;
	}
}

void changeNodeValue(node_t * list_head, unsigned int node_location, int node_value) // change the value of a node
{
	if (node_location < listLength(list_head)) // check if item exists
	{
		node_t * current_node;
		current_node = list_head;

		for (int i = 0; i < node_location; ++i) // go to the position
		{
			current_node = current_node->next;
		}

		current_node->value = node_value;
	}
}

node_t * insertNode(node_t * list_head, unsigned int node_location, int node_value) // insert at a certain point in the list
{
	node_t * current_node;
	node_t * new_node;
	current_node = list_head;

	// create new node
	new_node = malloc(sizeof(node_t));
	new_node->value = node_value;

	if (node_location >= listLength(list_head)) // append to the end
	{
		while (current_node->next != NULL) // go to the end of the list
		{
			current_node = current_node->next;
		}
		// point new node
		new_node->next = NULL;
		// point the last node to the current node
		current_node->next = new_node;
		return list_head; // return the header
	}
	else if (node_location == 0) // new node becomes head
	{
		new_node->next = list_head;
		return new_node;
	}
	else // insert in the middle
	{
		for (int i = 0; i < node_location - 1; ++i) // goto the correct node
		{
			current_node = current_node->next;
		}
		// point new node
		new_node->next = current_node->next;
		// point the last node to the current node
		current_node->next = new_node;
		return list_head; // return the header
	}
}

node_t *  destroyNode(node_t * list_head, unsigned int node_location) // destroy a node
{
	node_t * current_node;

	if (node_location < listLength(list_head) && node_location != 0) // check if item exists
	{
		node_t * node_to_delete, * prev_node, * next_node;
		current_node = list_head;

		for (int i = 0; i < node_location - 1; ++i) // go to the prior to the node
		{
			current_node = current_node->next;
		}
		// find addressees for nodes around the the node being removed
		prev_node = current_node;
		current_node = current_node->next;
		node_to_delete = current_node;
		next_node = node_to_delete->next;
		prev_node->next = next_node; // remove the node to delete from the chain
		free(node_to_delete); // destroy the node
	}
	else if (node_location == 0) // if the head is being deleted
	{
		current_node = list_head->next;
		free(list_head);
		return current_node;
	}

	return list_head;
}

void destroyList(node_t * list_head) // free the entire list 
{
	node_t * current_node;
	current_node = list_head;

	while (current_node->next != NULL)
	{
		list_head = current_node;
		current_node = current_node->next;
		free(list_head);
	}
	list_head = current_node;
	current_node = current_node->next;
	free(list_head);
}

int main() 
{
    node_t * head;
    int initial_list[6] = {2, 3, 7, 4, 4, 6};
    head = newList(6, initial_list);
    head = insertNode(head, 0, 1);
    head = destroyNode(head, 3);
    changeNodeValue(head, 4, 5);

    // Print list
    for (int i = 0; i < listLength(head); ++i)
    {
    	printf("%d\n", getNodeValue(head, i));
    }

    destroyList(head);
    
    return 0;
}