c-在双链表中添加和删除元素

Question

我写了一个代码，用于添加和删除双链表。首先，我按顺序添加元素并打印，它就可以工作了。然后我删除元素，并考虑不在列表中的元素；找不到号码"；。关于其他元素我只能删除300个其他元素不能删除。问题出在哪里？

#include<stdio.h>    
#include<stdlib.h>    
//Doubly Linked List                
struct n{    
int x;   
struct n * next;  
struct n * prev;  
}; 
typedef struct n node;       
void print(node * r){    
while(r!=NULL){  
printf("%d ", r->x);    
r=r->next;    
}    
printf("n");    
}    
node * addSeq(node * r, int x){    
if(r==NULL){//if linkedlist is empty, makes a node and puts an element    
r=(node *)malloc(sizeof(node));    
r->next=NULL;    
r->prev=NULL;//as well as next prev must point to NULL    
r->x=x;    
return r;    
}           
if(r->x > x){//if not empty but less than first element root changes        
node * temp = (node *)malloc(sizeof(node));    
temp->x = x;    
temp->next=r;    
r->prev=temp;    
return temp;    
}    
node * iter = r;    
while(iter->next!=NULL && iter->next->x < x){    
iter=iter->next;    
}    
node * temp = (node *)malloc(sizeof(node));    
temp->next = iter->next;    
iter->next=temp;    
temp->prev=iter;    
if(temp->next!=NULL)    
temp->next->prev=temp;    
temp->x=x;    
return r;    
}    
node * delete(node *r, int x){    
node *temp;    
node *iter = r;     
if(r->x == x){    
temp = r;    
r = r->next;    
free(temp);    
return r;    
}    
while(iter->next != NULL && iter->next->x != x){    
iter = iter->next;    
}    
if(iter->next==NULL){    
printf("Number was not found n");    
return r;    
}    
temp = iter->next; //iter points to the element that is previous of the element which we want     
//to delete    
iter->next = iter->next->next;       
iter->next->prev=iter;//temp is the element that we want to delete    
free(temp);    
return r;    
}    
int main(){    
node * root;    
root = NULL;    
root=addSeq(root, 400);    
root=addSeq(root, 350);    
root=addSeq(root, 500);    
root=addSeq(root, 450);    
root=addSeq(root, 300);     
print(root);    
root=delete(root, 410);    
print(root);//Cannot find number and prints the elements    
root=delete(root, 300);    
print(root);    
root=delete(root, 500);    
print(root);    
root=delete(root, 350);    
print(root);    
}    

Answer 1

当要删除的节点不是列表中的第一个时，执行以下代码：

temp = iter->next; //iter points to the element that is previous of the element which we want     
//to delete    
iter->next = iter->next->next;       
iter->next->prev=iter;//temp is the element that we want to delete

考虑一下当这个节点iter->next是列表中的最后一个时会发生什么。则iter->next->nexzt为空，并且iter->next = iter->next->next;将iter->next设置为空。然后iter->next->prev尝试取消引用该空指针。

您必须更改代码处理列表中最后一个节点的方式。