节点未被删除 [英] Node not being deleted

问题描述

伙计我试图删除节点2，但程序没有进入if循环进行比较。第一个打印f甚至不打印！请帮忙！

 #include< stdio.h> 
 #include< stdlib.h> 
 
  struct  dll {
  struct  dll * prev; 
  int 数据; 
  struct  dll * next; 
}; 
 
  int  main（）{
  struct  dll * p1， * p2，* p3，* temp; 
 p1 = malloc（ sizeof （ struct  dll））; 
 p2 = malloc（ sizeof （ struct  dll））; 
 p3 = malloc（ sizeof （ struct  dll））; 
 p1-> prev = NULL; 
 p1-> data =  1 ; 
 p1-> next = p2; 
 p2-> prev = p1; 
 p2-> data =  2 ; 
 p2-> next = p3; 
 p3-> prev = p2; 
 p3-> data =  3 ; 
 p3-> next = NULL; 
  struct  dll *  add  = NULL; 
  int  count =  0 ; 
 printf（ 添加p1 ::％p添加p2 ::％p添加p3 :: ％p \ n，p1，p2，p3）; 
  for （temp = p1; temp！= NULL; temp = temp-> next）{
 count ++; 
} 
 printf（  no节点％d \ n，计数）; 
  //   puts（输入节点的地址以删除它）;  
  add  =& p2; 
 printf（ 我要删除的节点的地址::％p \ n ，*加）; 
 temp = p1; 
 printf（  temp：％p \ n，temp）; 
  while （temp！= NULL）{
  if （temp-> next ==  add ）{
 printf（  temp for for循环：％p \ n，temp）; 
 temp-> next = temp-> next-> next; 
 temp-> next-> next-> prev = temp; 
 printf（ ％p％p \ n，temp-> next， TEMP->下一步 - >下一步 - >分组）; 
 free（temp）; 
 temp = NULL; 
} 
 temp = temp-> next; 
  break ; 
} 
 puts（ 删除后尝试）; 
 
 count =  0 ; 
  for （p1; p1！= NULL; p1 = p1-> next）{
 count ++; 
} 
 printf（  no节点％d \ n，计数）; 
免费（p1）; 
 p1 = NULL; 
免费（p2）; 
 p2 = NULL; 
免费（p3）; 
 p3 = NULL; 
  return   0 ; 
} 

输出：

添加p1 :: 0x8512008添加p2 :: 0x8512018添加p3 :: 0x8512028< br /> 
没有节点3< br /> 
节点的地址我要删除:: 0x8512018< br /> 
 temp：0x8512008< br /> 
删除后尝试< br /> 
 no of nodes 3 

解决方案

您好Jeevan83



问题与此声明有关

add =& p2; //这将指定指针p2的地址，但你想指定指针p2指向的地址，所以使用 add = p2 ;



另外printf（地址我要删除的节点::％p \ n， * add ）;

这是语法错误你想要打印地址所以只使用添加而不是 *添加



供您参考

您的代码只有在删除2节点时才能正常运行如果您尝试删除其他节点，它将因分段错误而失败。尝试对于那些情况，如果需要在这里发布。感谢

Guys I am trying to delete node 2 but program is not entering the if loop for comparison. The first print f doesn’t print even! Please help!

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

struct dll {
    struct dll* prev;
    int data;
    struct dll* next;
};

int main() {
    struct dll* p1, *p2, *p3, *temp;
    p1 = malloc(sizeof(struct dll));
    p2 = malloc(sizeof(struct dll));
    p3 = malloc(sizeof(struct dll));
    p1->prev = NULL;
    p1->data = 1;
    p1->next = p2;
    p2->prev = p1;
    p2->data = 2;
    p2->next = p3;
    p3->prev = p2;
    p3->data = 3;
    p3->next = NULL;
    struct dll * add=NULL;
    int count = 0;
    printf("add of p1::%p add of p2::%p add of p3::%p \n",  p1, p2, p3);
for ( temp = p1; temp != NULL; temp = temp->next ){
        count++;
    }
    printf("no of nodes %d\n", count);
   //puts("enter the addresss of node to delete it");
    add=&p2;
printf("address of node which i wanna delete::%p\n",*add);
 temp = p1;
 printf("temp:%p\n",temp);
while(temp!=NULL){
        if (temp->next == add) {
        printf("temp in for loop:%p\n",temp);
            temp->next=temp->next->next;
            temp->next->next->prev=temp;
            printf("%p %p\n",temp->next,temp->next->next->prev);
            free(temp);
            temp = NULL;
        }
        temp = temp->next;
break;
    }
    puts("after deletion attempted");

count =0;
for ( p1; p1!= NULL; p1 = p1->next ){
        count++;
    }
    printf("no of nodes %d\n", count);
    free(p1);
    p1 = NULL;
    free(p2);
    p2 = NULL;
    free(p3);
    p3 = NULL;
    return 0;
}

Output:

add of p1::0x8512008 add of p2::0x8512018 add of p3::0x8512028<br />
no of nodes 3<br />
address of node which i wanna delete::0x8512018<br />
temp:0x8512008<br />
after deletion attempted<br />
no of nodes 3

解决方案

Hi Jeevan83

Problem is with this statement
add=&p2; //this will assign the address of pointer p2 but you want to assign address to which pointer p2 points to so use add=p2;

Also printf("address of node which i wanna delete::%p\n",*add);
This is syntax error You want to print the address so use only add instead of *add

For your information
Your code will only run properly when 2 node is deleted if u try to delete some other it will fail with segmentation fault. Try for that cases too if required post here . Thanks

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