gistfile1.txt

#include <stdio.h>

struct list_node
{
	int value;
	list_node* next;
	list_node( int value ) : value( value ), next( NULL ) {}
};

void insert_before( list_node** head, list_node* before_this, list_node* insert_this)
{
	if( *head == before_this ) {
		*head = insert_this;
		insert_this->next= before_this;
	}
	else {
		list_node* after_this = *head;
		while( after_this->next != before_this ) {
			after_this= after_this->next;
		}
		insert_this->next= after_this->next;
		after_this->next= insert_this;
	}
}

void push( list_node* head, list_node* node )
{
	while( head->next != NULL )
		head = head->next;
	head->next= node;
}

void test_print( list_node* head, const char* expected )
{
	while( head!= NULL ){
		printf( "%d ", head->value );
		head= head->next;
	}
	printf( "  (vs)\n%s\n\n", expected );
}

void test_append_to_single()
{
	list_node* list = new list_node( 1 );
	push( list, new list_node( 2 ) );
	test_print( list, "1 2" );
}

void test_prepend_to_single()
{
	list_node* list = new list_node( 1 );
	insert_before( &list, list, new list_node( 2 ) );
	test_print( list, "2 1" );
}

void test_prepend_to_multiple()
{
	list_node* list = new list_node( 1 );
	push( list, new list_node( 2 ) );
	list_node* third = new list_node( 3 );
	push( list, third );
	insert_before( &list, third, new list_node( 0 ) );
	test_print( list, "1 2 0 3" );
}



int main() {
	test_append_to_single();
	test_prepend_to_single();
	test_prepend_to_multiple();
}