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C Quellcode

#include<stdlib.h>
#include<stdio.h>
 
typedef struct _node{
	int *content;
	struct _node *prev;
	struct _node *next;
} node;
 
const int nsize = sizeof(node);
 
node* add( node *firstnode, void *cont ) {
 
	node *newnode = malloc( nsize );
	newnode->content = cont;
 
	if( firstnode == NULL ) { 	/*Wenn Liste leer*/
		newnode->prev = NULL;
		newnode->next = NULL;
		return newnode;
	}
 
	else{			/*fuege in bestehende Liste ein*/
		newnode->next = firstnode;
		newnode->prev = NULL;
		firstnode->prev= newnode;
		return newnode;
	}
}
 
node* add_ith( node *firstnode, void *cont, int pos ) {
 
	int i;
 
	node *newnode = malloc( nsize );
	newnode->content = cont;
 
	node *itnode = firstnode;	/*suche i-1te Position*/
	for( i=1 ; i< pos-1 ; i++ ) {
		itnode = itnode->next;
	}
 
	if( itnode == NULL)	/*Position ausserhalb, nicht einfuegen*/
		return firstnode;
 
	else{
		newnode->next = itnode->next;	/*fuege neuen Knoten ein*/
		newnode->prev = itnode;
		newnode->next->prev = newnode;
		itnode->next = newnode;
 
		return firstnode;
	}
}
 
node* add_last( node *firstnode, void *cont ){
 
	node *newnode = malloc( nsize );
	newnode->content = cont;
 
	node *itnode = firstnode;	/*suche letzten Knoten*/
	while( itnode->next != NULL ) {
		itnode = itnode->next;		
	}
	itnode->next = newnode;
	newnode->prev = itnode;
	newnode->next = NULL;
 
	return firstnode;
}
 
node* del( node *firstnode){
 
	if( firstnode == NULL || firstnode->next == NULL)	/*Wenn kein oder nur ein Konten vorhanden*/
		return NULL;
 
	else{
		node *newfirstnode = firstnode->next;
		newfirstnode->prev = NULL;
		free(firstnode);
		return newfirstnode;
	}
}
 
node* del_ith( node *firstnode, int pos ){
 
	int i;
 
	node *itnode = firstnode;
 
	for( i=1 ; i< pos-1 ; i++ ){	/*suche i-1te Position*/
		itnode = itnode->next;
	}
 
	if( itnode == NULL || itnode->next == NULL)	/*wenn knoten nicht vorhanden*/
		return firstnode;
 
	else{
		node *delnode = itnode->next;	/*merke zu loeschenden Knoten*/
		itnode->next = delnode->next;
		delnode->next->prev = itnode;
		free(delnode);
		return firstnode; 
	}
}
 
node* del_last( node *firstnode){
 
	node *itnode = firstnode;
 
	while( itnode->next->next != NULL )	/*suche vorletzten Knoten*/
		itnode = itnode->next;
 
	free(itnode->next);
	itnode->next = NULL;
	return firstnode;
}
 
void del_all( node *firstnode ) {
	node *delnode = firstnode;
 
	while( firstnode->next != NULL ){
		firstnode = firstnode->next;
		free( delnode );
		delnode = firstnode;
	}
 
	free( delnode );
}
 
int main(void){
	int i1 = 0;
	int i2 = 1;
	int i3 = 2;
	void *eins = &i1;
	void *zwei = &i2;
	void *drei = &i3;
 
	node *dvlist = NULL;
	dvlist = add(dvlist,eins);
	dvlist = add(dvlist,zwei);
	dvlist = add_ith(dvlist,drei,2);
 
	printf("%d,%d,%d\n", *(dvlist->content), *(dvlist->next->content), *(dvlist->next->next->content));
 
	del_all(dvlist);
 
	return 1;
}