Simple linked list implementation source code

This snippet submitted by yzb3 on 2012-03-23. It has been viewed 43620 times.
Rating of 5.6 with 178 votes
/*
	Simple singly linked lists example usage; it is only one of 
	many possible implementations - try your own enchancements.
*/

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

typedef int stack_data; //stack data type - set for integers, modifiable
typedef struct stack Node; //short name for the stack type
struct stack //stack structure format
{
	stack_data data;
	Node *next;
};

int stack_len(Node *node_head); //stack length
void stack_push(Node **node_head, stack_data d); //pushes a value d onto the stack
stack_data stack_pop(Node **node_head); //removes the head from the stack & returns its value
void stack_print(Node **node_head); //prints all the stack data
void stack_clear(Node **node_head); //clears the stack of all elements
void stack_snoc(Node **node_head, stack_data d); //appends a node
int stack_elem(Node **node_head, stack_data d); //checks for an element

int main(void)
{
	Node *node_head = NULL; //pointer to stack head

	//example usage:
	stack_push(&node_head, 7); //push value 7 onto stack
	printf("%d\n", node_head -> data); //show stack head value
	stack_push(&node_head, 21); //push value 21 onto stack
	stack_print(&node_head); //print the stack
	if(stack_elem(&node_head, 7)) puts("found 7"); //does 7 belong to the stack?
	stack_snoc(&node_head, 0); //append 0 to the end of the stack
	stack_print(&node_head); //print the stack
	printf("%d\n", stack_pop(&node_head)); //pop the stack's head
	stack_print(&node_head); //print the stack
	stack_clear(&node_head); //clear the stack
	stack_print(&node_head); //print the stack
	
	getchar();
	return 0;
}

int stack_len(Node *node_head)
{
	Node *curr = node_head;
	int len = 0;
	
	while(curr)
	{
		++len;
		curr = curr -> next;
	}
	return len;
}

void stack_push(Node **node_head, stack_data d)
{
	Node *node_new = malloc(sizeof(Node));
	
	node_new -> data = d;
	node_new -> next = *node_head;
	*node_head = node_new;
}

stack_data stack_pop(Node **node_head)
{
	Node *node_togo = *node_head;
	stack_data d;
	
	if(node_head)
	{
		d = node_togo -> data;
		*node_head = node_togo -> next;
		free(node_togo);
	}
	return d;
}

void stack_print(Node **node_head)
{
	Node *node_curr = *node_head;
	
	if(!node_curr)
		puts("the stack is empty");
	else
	{
		while(node_curr)
		{
			printf("%d ", node_curr -> data); //set for integers, modifiable
			node_curr = node_curr -> next;
		}
		putchar('\n');
	}
}

void stack_clear(Node **node_head)
{
	while(*node_head)
		stack_pop(node_head);
}

void stack_snoc(Node **node_head, stack_data d)
{
	Node *node_curr = *node_head;
	
	if(!node_curr)
		stack_push(node_head, d);
	else
	{
		//find the last node
		while(node_curr -> next)
			node_curr = node_curr -> next;
		//build the node after it
		stack_push(&(node_curr -> next), d);
	}
}

int stack_elem(Node **node_head, stack_data d)
{
	Node *node_curr = *node_head;
	
	while(node_curr)
	{
		if(node_curr -> data == d) //set for numbers, modifiable
			return 1;
		else
			node_curr = node_curr -> next;
	}
	return 0;
}
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