数据结构的双向循环链表

Question

作答和题目都在下面，想问问为什么这样写是错误的，用debug看到每一句都有运行，但是结果事实上结果却是不如意的

Answer 1

仅供参考：

//不带表头结点的循环双向链表
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <time.h>
#include <locale.h>
struct NODE {
    int          data;
    struct NODE *next;
    struct NODE *prev;
} *head,*p,*q,*s,*p1,*p2,*q1,**ta;
int i,k,n,t,m,v,N=10;
int main() {
    setlocale(LC_ALL,"chs");
    srand(time(NULL));

    head=NULL;

    printf("创建%d个节点的循环双向链表:",N);//创建N个节点的循环双向链表
    p=head;
    for (i=0;i<N;i++) {
        q=(struct NODE *)malloc(sizeof(struct NODE));
        if (NULL==q) exit(1);
        q->data=rand()%100;//填写0..99的随机值
        q->next=NULL;
        q->prev=NULL;
        if (NULL==p) {
            head=q;
            p=head;
        } else {
            p->next=q;
            q->prev=p;
            p=q;
        }
    }
    p->next=head;
    head->prev=p;

    //输出整个循环双向链表
    s=head;
    while (1) {
        if (NULL==s) {
            printf("\n");
            break;
        }
        printf("%02d(=)",s->data);
        if (NULL!=s->next && s->next->prev!=s) {printf(" !\n");break;}
        s=s->next;
        if (s==head) {
            printf(" Loop\n");
            break;
        }
    }

    k=3;
    v=5;
    printf("将值为%d的结点插入到循环双向链表的第%d个结点前:",v,k);//将值为v的结点插入到循环双向链表的第k个结点前
    n=0;
    p=head;
    while (1) {
        if (NULL==p) {
            break;
        }
        n++;
        if (k==1) {
            q=(struct NODE *)malloc(sizeof(struct NODE));
            if (NULL==q) exit(1);
            q->data=v;
            q->next=head;
            q->prev=head->prev;
            head->prev->next=q;
            head->prev=q;
            head=q;
            break;
        } else {
            if (k-1==n) {
                q=(struct NODE *)malloc(sizeof(struct NODE));
                if (NULL==q) exit(1);
                q->data=v;
                q->next=p->next;
                q->prev=p;
                p->next->prev=q;
                p->next=q;
                break;
            }
        }
        p=p->next;
        if (p==head) break;
    }

    //输出整个循环双向链表
    s=head;
    while (1) {
        if (NULL==s) {
            printf("\n");
            break;
        }
        printf("%02d(=)",s->data);
        if (NULL!=s->next && s->next->prev!=s) {printf(" !\n");break;}
        s=s->next;
        if (s==head) {
            printf(" Loop\n");
            break;
        }
    }

    k=5;
    printf("删除第%d个节点:",k);//删除第k个节点
    n=0;
    p=head;
    while (1) {
        if (NULL==p) {
            break;
        }
        n++;
        if (k==1) {
            q=head;
            head=head->next;
            head->prev=q->prev;
            q->prev->next=head;
            if (q==head) head=NULL;
            free(q);
            break;
        } else {
            if (k-1==n) {
                q=p->next;
                p->next=q->next;
                q->next->prev=p;
                free(q);
                break;
            }
        }
        p=p->next;
        if (p==head) break;
    }

    //输出整个循环双向链表
    s=head;
    while (1) {
        if (NULL==s) {
            printf("\n");
            break;
        }
        printf("%02d(=)",s->data);
        if (NULL!=s->next && s->next->prev!=s) {printf(" !\n");break;}
        s=s->next;
        if (s==head) {
            printf(" Loop\n");
            break;
        }
    }

    printf("从小到大排序:");//从小到大排序
    for (p=head;p!=NULL;) {
        p1=p->prev;
        for (q=p->next,q1=p;q!=NULL;) {
            if (p->data > q->data) {

                //交换data
//              printf("swap %02d %02d\n",p->data,q->data);
//              t=p->data;p->data=q->data;q->data=t;

                //或者

                //交换prev和next
//              printf("swap %02d %02d\n",p->data,q->data);
                if (p==head) {//p是头
                    if (p->next==q) {//pq挨着
                        head=q;
                        head->prev=p1;
                        p1->next=q;
                        p->next=q->next;
                        p->prev=q;
                        q->next->prev=p;
                        q->next=p;
                        q=p;
                        p=head;
                    } else {//pq不挨着
                        head=q;
                        head->prev=p1;
                        p1->next=q;
                        p2=p->next;
                        p->next=q->next;
                        p->next->prev=p;
                        p->prev=q1;
                        q->next->prev=p;
                        q->next=p2;
                        p2->prev=q;
                        q1->next=p;
                        q=p;
                        p=head;
                    }
                } else {//p不是头
                    if (p->next==q) {//pq挨着
                        p1->next=q;
                        p->next=q->next;
                        p->prev=q;
                        q->next->prev=p;
                        q->next=p;
                        q->prev=p1;
                        q=p;
                        p=p1->next;
                    } else {//pq不挨着
                        p1->next=q;
                        p2=p->next;
                        p->next=q->next;
                        p->prev=q->prev;
                        q->next->prev=p;
                        q->next=p2;
                        q->prev=p1;
                        p2->prev=q;
                        q1->next=p;
                        q=p;
                        p=p1->next;
                    }
                }

                //输出整个循环双向链表
//              s=head;
//              while (1) {
//                  if (NULL==s) {
//                      printf("\n");
//                      break;
//                  }
//                  printf("%02d(=)",s->data);
//                  if (NULL!=s->next && s->next->prev!=s) {printf(" !\n");break;}
//                  s=s->next;
//                  if (s==head) {
//                      printf(" Loop\n");
//                      break;
//                  }
//              }
//              printf("head,p,q:%02d %02d %02d\n",head->data,p->data,q->data);
//              getchar();
            }
            q1=q;q=q->next;
            if (q==head) break;
        }
        p=p->next;
        if (p->next==head) break;
    }

    //输出整个循环双向链表并计算链表长度n
    n=0;
    s=head;
    while (1) {
        if (NULL==s) {
            printf("\n");
            break;
        }
        printf("%02d(=)",s->data);
        if (NULL!=s->next && s->next->prev!=s) {printf(" !\n");break;}
        n++;
        s=s->next;
        if (s==head) {
            printf(" Loop\n");
            break;
        }
    }

    printf("将整个链表逆序:");//将整个链表逆序
    if (n>=2) {
        p=head;
        while (1) {
            q=p->prev;p->prev=p->next;p->next=q;
            p=p->next;
            if (p==head) break;
        }
    }

    //输出整个循环双向链表
    s=head;
    while (1) {
        if (NULL==s) {
            printf("\n");
            break;
        }
        printf("%02d(=)",s->data);
        if (NULL!=s->next && s->next->prev!=s) {printf(" !\n");break;}
        s=s->next;
        if (s==head) {
            printf(" Loop\n");
            break;
        }
    }

    m=4;
    n=6;
    printf("将循环双向链表中前%d个结点和后%d个结点进行互换:",m,n);//将循环双向链表中前m个结点和后n个结点进行互换,m+n为链表总长
    k=0;
    p=head;
    while (1) {
        if (NULL==p) {
            break;
        }
        k++;
        if (m==k) {
            q=p;
            break;
        }
        p=p->next;
        if (p==head) break;
    }
    head=q->next;

    //输出整个循环双向链表
    s=head;
    while (1) {
        if (NULL==s) {
            printf("\n");
            break;
        }
        printf("%02d(=)",s->data);
        if (NULL!=s->next && s->next->prev!=s) {printf(" !\n");break;}
        s=s->next;
        if (s==head) {
            printf(" Loop\n");
            break;
        }
    }

    //释放所有节点
    p=head;
    while (1) {
        if (NULL==p) {
            break;
        }
        q=p->next;
        free(p);
        p=q;
        if (p==head) {
            break;
        }
    }

    return 0;
}
//创建10个节点的循环双向链表:12(=)46(=)31(=)63(=)25(=)91(=)39(=)02(=)92(=)68(=) Loop
//将值为5的结点插入到循环双向链表的第3个结点前:12(=)46(=)05(=)31(=)63(=)25(=)91(=)39(=)02(=)92(=)68(=) Loop
//删除第5个节点:12(=)46(=)05(=)31(=)25(=)91(=)39(=)02(=)92(=)68(=) Loop
//从小到大排序:02(=)05(=)12(=)25(=)31(=)39(=)46(=)68(=)91(=)92(=) Loop
//将整个链表逆序:92(=)91(=)68(=)46(=)39(=)31(=)25(=)12(=)05(=)02(=) Loop
//将循环双向链表中前4个结点和后6个结点进行互换:39(=)31(=)25(=)12(=)05(=)02(=)92(=)91(=)68(=)46(=) Loop
//