程序代码：

root@~ #cat dl.c
#include <stdio.h>
struct entry {
        int val;
        struct entry *next; //后继
        struct entry *prev; //前驱
};

int main (void) {
        struct entry n1,n2,n3,n4,*s=&n4; //定义4个结构变量，指针s指向第四个结点（要删除n3）
//定义一些测试数据
        n1.val=100; n1.next=&n2; n1.prev=0;
        n2.val=200; n2.next=&n3; n2.prev=&n1;
        n3.val=300; n3.next=&n4; n3.prev=&n2;
        n4.val=400; n4.next=0;   n4.prev=&n3;
//打印原始数据
        printf("Before delete:\n%i\n%i\n%i\n%i\n\n",n1.val,n1.next->val,n2.next->val,n3.next->val);
//将s指针指向要删除结点的上一个结点
        s->prev->prev->next=s;
//打印删除后的链表
        printf("After delete:\n");
//定义一个表头，便于遍历
        struct entry *h=&n1;
        while(h) {
                printf("%i\n",h->val);
                h=h->next;
        }
        return 0;
}

root@~ #./dl
Before delete:
100
200
300
400

After delete:
100
200
400
root@~ #