C语言实现的循环单链表功能示例

#ifndef __SCLIST_H__#define __SCLIST_H__#include<cstdio>#include<malloc.h>#include<assert.h>typedef int ElemType;typedef struct Node {  ElemType data;  struct Node *next;}Node,*PNode;typedef struct List {  PNode first;  PNode last;  size_t size;}List;void InitSClist(List *list);//初始化循环单链表void push_back(List *list, ElemType x);//在循环单链表的末尾插入元素void push_front(List *list, ElemType x);//在循环单链表的头部插入元素void show_list(List *list);//打印循环单链表void pop_back(List *list);//删除循环单链表的最后一个元素void pop_front(List *list);//删除循环单链表的第一个元素void insert_val(List *list, ElemType val);//将数据元素插入到循环单链表中（要求此时循环单链表中的数据元素顺序排列）Node* find(List *list, ElemType x);//查找循环单链表中数据值为x的结点int length(List *list);//求循环单链表的长度void delete_val(List *list, ElemType x);//按值删除循环单链表中的某个数据元素void sort(List *list);//对循环单链表进行排序void reverse(List *list);//逆置循环单链表void clear(List *list);//清除循环单链表void destroy(List *list);//摧毁循环单链表//优化Node* _buynode(ElemType x);//创建结点#endif

#include"SClist.h"Node* _buynode(ElemType x) {  Node *s = (Node*)malloc(sizeof(Node));  assert(s != NULL);  s->data = x;  s->next = NULL;  return s;}void InitSClist(List *list) {  Node *s = (Node*)malloc(sizeof(Node));  assert(s != NULL);  list->first = list->last = s;  list->last->next = list->first;//让链表最后一个结点的指针域指向头结点，从而时链表循环  list->size = 0;}void push_back(List *list, ElemType x) {  Node *s = _buynode(x);  list->last->next = s;  list->last = s;  list->last->next = list->first;  list->size++;}void push_front(List *list, ElemType x) {  Node *s = _buynode(x);  s->next = list->first->next;  list->first->next = s;  if (list->last == list->first)    list->last = s;  list->size++;}void show_list(List *list) {  Node *p = list->first->next;  while (p != list->first) {    printf("%d->", p->data);    p = p->next;  }  printf("Nul./n");}void pop_back(List *list) {  if (list->size == 0) return;  Node *p = list->first;  while (p->next != list->last)    p = p->next;  free(list->last);  list->last = p;  list->last->next = list->first;  list->size--;}void pop_front(List *list) {  if (list->size == 0) return;  Node *p = list->first->next;  list->first->next = p->next;  if (list->size == 1)    list->last = list->first;  free(p);  list->size--;}void insert_val(List *list, ElemType x) {  Node *p = list->first;  while (p->next != list->last && p->next->data < x)    p = p->next;  if (p->next == list->last && p->next->data < x)    push_back(list, x);  else {    Node *s = _buynode(x);    s->next = p->next;    p->next = s;    list->size++;  }}Node* find(List *list, ElemType key) {  if (list->size == 0) return NULL;  Node *p = list->first->next;  while(p != list->first && p->data != key)    p = p->next;  if (p == list->first)    return NULL;  return p;}int length(List *list) {  return list->size;}void delete_val(List *list, ElemType x) {  if (list->size == 0) return;  Node *p = find(list, x);  if (p == NULL) {    printf("没有要删除的数据!/n");    return;  }  if (p == list->last)    pop_back(list);  else {    Node *q = p->next;    p->data = q->data;    p->next = q->next;    free(q);    list->size--;  }}void sort(List *list) {  if (list->size == 0 || list->size == 1) return;  Node *s = list->first->next;  Node *q = s->next;  list->last->next = NULL;  list->last = s;  list->last->next = list->first;  while (q != NULL) {    s = q;    q = q->next;    Node *p = list->first;    while (p->next != list->last && p->next->data < s->data)      p = p->next;    if (p->next == list->last &&p->next->data < s->data) {      list->last->next = s;      list->last = s;      list->last->next = list->first;    }    else {      s->next = p->next;      p->next = s;    }  }}void reverse(List *list) {  if (list->size == 0 || list->size == 1) return;  Node *p = list->first->next;  Node *q = p->next;  list->last->next = NULL;  list->last = p;  list->last->next = list->first;  while (q != NULL) {    p = q;    q = q->next;    p->next = list->first->next;    list->first->next = p;  }}void clear(List *list) {  Node *p = list->first->next;  while (p != list->first) {    list->first->next = p->next;    free(p);    p = list->first->next;  }  list->last = list->first;  list->last->next = list->first;  list->size = 0;}void destroy(List *list) {  clear(list);  free(list->first);  list->first = list->last = NULL;}

#include"SClist.h"void main() {  List mylist;  InitSClist(&mylist);  ElemType item;  Node *p = NULL;  int select = 1;  while (select) {    printf("*******************************************/n");    printf("*[1] push_back    [2] push_front  */n");    printf("*[3] show_list    [4] pop_back   */n");    printf("*[5] pop_front    [6] insert_val  */n");    printf("*[7] find       [8] length    */n");    printf("*[9] delete_val    [10] sort     */n");    printf("*[11] reverse     [12] clear     */n");    printf("*[13*] destroy     [0] quit_system  */n");    printf("*******************************************/n");    printf("请选择：>>");    scanf("%d", &select);    if (select == 0) break;    switch (select) {    case 1:      printf("请输入要插入的数据（-1结束）:>");      while (scanf("%d", &item), item != -1) {        push_back(&mylist, item);      }      break;    case 2:      printf("请输入要插入的数据（-1结束）:>");      while (scanf("%d", &item), item != -1) {        push_front(&mylist, item);      }      break;    case 3:      show_list(&mylist);      break;    case 4:      pop_back(&mylist);      break;    case 5:      pop_front(&mylist);      break;    case 6:      printf("请输入要插入的数据:>");      scanf("%d", &item);      insert_val(&mylist, item);      break;    case 7:      printf("请输入要查找的数据:>");      scanf("%d", &item);      p = find(&mylist, item);      if (p == NULL)        printf("要查找的数据在单链表中不存在！/n");      break;    case 8:      printf("单链表的长度为%d/n", length(&mylist));      break;    case 9:      printf("请输入要删除的值:>");      scanf("%d", &item);      delete_val(&mylist, item);      break;    case 10:      sort(&mylist);      break;    case 11:      reverse(&mylist);      break;    case 12:      clear(&mylist);      break;      //case 13:      //destroy(&mylist);      //break;    default:      printf("选择错误,请重新选择！/n");      break;    }  }  destroy(&mylist);}