c/c++ 线性表之双向循环链表
c/c++ 线性表之双向循环链表
线性表之双向循环链表
不是存放在连续的内存空间，链表中的每个节点的next都指向下一个节点，每个节点的before都指向前一个节点，最后一个节点的下一个节点不是NULL，是头节点。
真实的第一个节点是头节点，头节点不存放数据，单纯为了编写程序方便。但是下面注释里写的【第一个节点】的含义是头节点的下一节点，也就是真实存放数据的第一个节点。
下面的代码实现了以下功能
| 函数 | 功能描述 |
|---|---|
| push_back | 从链表的最后插入节点 |
| push_front | 从链表的起始插入节点 |
| show_list | 打印出链表里每个节点的值 |
| pop_back | 删除链表最后一个节点 |
| pop_front | 删除链表起始节点 |
| insert_val | 在合适的位置插入一个节点； 比如原来的链表:1->3->NULL，当要插入的节点的值为2的时候，就会在1和3之间插入这个节点，插入后的链表：1->2->3->NULL |
| find | 查找指定的节点 |
| length | 返回链表中节点的个数 |
| delete_val | 删除指定的节点 |
| sort | 排序，重新排列节点 |
| resver | 按倒序，重新排列节点 |
| clear | 释放除了头节点之外的所有节点所占用的内存空间 |
| destroy | 释放所有节点的所占用的内存空间，包括头节点 |
whileshuangnode.h
#ifndef __WHILESHUANGNODE__
#define __WHILESHUANGNODE__
#include <stdio.h>
#include <malloc.h>
#include <assert.h>
#include <memory.h>
#include <stdbool.h>
#define ElemType int
typedef struct Node{
ElemType data;
struct Node* before;
struct Node* next;
}Node;
typedef struct NodeList{
Node* first;
Node* last;
size_t size;
}NodeList;
void init(NodeList*);
void push_back(NodeList*, ElemType);
void push_front(NodeList*, ElemType);
void pop_back(NodeList*);
void pop_front(NodeList*);
void show_list(NodeList*);
void insert_val(NodeList*, ElemType);
Node* find(NodeList*, ElemType);
void delete_val(NodeList*, ElemType);
void sort(NodeList*);
void sort1(NodeList*);
void resver(NodeList*);
void resver1(NodeList*);
void resver2(NodeList*);
void clear(NodeList*);
void destroy(NodeList*);
#endif
whileshuangnode.c
#include "whileshuangnode.h"
void init(NodeList* list){
list->first = (Node*)malloc(sizeof(Node));
list->last = list->first;
list->first->before = list->last;
list->last->next = list->first;
list->size = 0;
}
Node* create_node(ElemType val){
Node* node = (Node*)malloc(sizeof(Node));
assert(NULL != node);
node->data = val;
node->before = NULL;
node->next = NULL;
return node;
}
void push_back(NodeList* list, ElemType val){
Node* p = create_node(val);
p->before = list->last;
p->next = list->first;
list->first->before = p;
list->last->next = p;
list->last = p;
list->size++;
}
void push_front(NodeList* list, ElemType val){
Node* p = create_node(val);
//设置p的before和next
p->before = list->first;
//第一次添加节点的时候要移动未指针,还要设置first的before
if(list->first == list->first->next){
list->last = p;
p->next = list->first;
list->first->before = p;
}
//不是第一次添加节点的时候，要把原第一个节点的before指向，新添加的节点
else{
p->next = list->first->next;
list->first->next->before = p;
}
//设置头指针的next节点
list->first->next = p;
list->size++;
}
void show_list(NodeList* list){
Node* tmp = list->first->next;
while(tmp != list->first){
printf("%d->", tmp->data);
tmp = tmp->next;
}
printf("NULL\n");
}
void pop_back(NodeList* list){
if(list->size == 0)return;
free(list->last);
//让尾指针的next指向NULL
list->last->before->next = list->first;
//让first的before指向新的尾节点
list->first->before = list->last->before;
//让尾指针指向原尾节点的前一个节点
list->last = list->last->before;
list->size--;
}
void pop_front(NodeList* list){
if(list->size == 0)return;
free(list->first->next);
//就剩一个节点的时候，要移动尾指针。
if(list->first->next == list->last){
list->last = list->first;
list->last->next = list->first;
list->first->before = list->last;
list->size--;
return;
}
//头指针的next指向第二个节点
list->first->next = list->first->next->next;
//第二个节点的before指向头节点
list->first->next->before = list->first;
list->size--;
}
void insert_val(NodeList* list, ElemType val){
Node* n = create_node(val);;
Node* p = list->first;
while(p->next != list->first && val > p->next->data){
p = p->next;
}
//第一次加节点，或者，最后一个节点的值也没有比给的值大的时候
if(list->first == p->next){
n->next = list->first;
n->before = list->last;
list->last->next = n;
list->first->before = n;
list->last = n;
list->size++;
return;
}
//新节点的next指向原节点的下一个节点
n->next = p->next;
//原节点的next指向新节点，注意这句的位置必须在上句的下面
p->next = n;
//新节点的下一个节点的before指向新节点
n->next->before = n;
//新节点的before指向原节点
n->before = p;
list->size++;
}
//寻找给定值的节点的位置
Node* find(NodeList* list, ElemType val){
if(list->size == 0)return NULL;
Node* p = list->first;
while(p->next != list->first && p->next->data != val){
p = p->next;
}
if(list->first == p->next){
return NULL;
}
printf("%d is found\n", p->next->data);
return p->next;
}
void delete_val(NodeList* list, ElemType val){
Node* p = find(list, val);
if(NULL == p) return;
//删除的节点是尾节点的时候，要移动last
if(p == list->last){
list->last = p->before;
p->before->next = list->first;
list->first->before = p->before;
list->size--;
return;
}
p->before->next = p->next;
p->next->before = p->before;
free(p);
list->size--;
}
void sort(NodeList* list){
if(list->size == 1 || list->size == 0)return;
//p为第一个节点
Node* p = list->first->next;
//ｔ是空白list，往t里加节点
Node* t = list->first;
list->last = list->first;
list->last->next = list->first;
list->first->before = list->last;
size_t sz = list->size;
Node* tmp;
while(sz-- > 0){
//p的next会被改变，所以提前保存
tmp = p->next;
while(t->next != list->first && p->data > t->next->data){
t = t->next;
}
//ｔ为first，或者t为last,都是尾插
if(t->next == list->first){
t->next = p;
p->next = list->first;
p->before = t;
list->first->before = p;
list->last = p;
}
else{
p->next = t->next;
t->next->before = p;
t->next = p;
p->before = t;
}
p = tmp;
t = list->first;
}
}
void resver(NodeList* list){
if(list->size == 1 || list->size == 0)return;
//第一个节点
Node* head = list->first->next;
//第二个节点
Node* second = head->next;
//head就是last，所以要head->next = NULL;
list->last = head;
list->last->next = list->first;
list->first->before = list->last;
Node* tmp;
while(second != list->first){
//必须保存second的next，因为下面的代码，会改变second的next
tmp = second->next;
//头插
second->next = list->first->next;
list->first->next->before = second;
list->first->next = second;
second->before = list->first;
second = tmp;
}
}
void clear(NodeList* list){
Node* p = list->first->next;
while(p != list->last){
p = p->next;
free(p);
}
list->last = list->first;
list->last->next = list->first;
list->first->before = list->last;
list->size = 0;
}
void destroy(NodeList* list){
clear(list);
free(list->first);
}
whileshuangnodemain.c
#include "whileshuangnode.h"
int main(){
NodeList list;
init(&list);
int select = 1;
ElemType item;
Node* node = NULL;
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] sort [12] resver ***\n");
printf("*** [13] [14] clear ***\n");
printf("*** [0] quit [15*]destroy ***\n");
printf("*****************************************\n");
printf("请选择:>");
scanf("%d", &select);
if(0 == select)
break;
switch(select){
case 1:
printf("请输入要插入的数据,以-1结束>\n");
while(scanf("%d",&item) && item != -1){
push_back(&list, item);
}
show_list(&list);
break;
case 2:
printf("请输入要插入的数据,以-1结束>\n");
while(scanf("%d", &item) && item != -1){
push_front(&list, item);
}
show_list(&list);
break;
case 3:
show_list(&list);
break;
case 4:
pop_back(&list);
show_list(&list);
break;
case 5:
pop_front(&list);
show_list(&list);
break;
case 6:
printf("请输入要插入的数据>\n");
scanf("%d",&item);
insert_val(&list, item);
show_list(&list);
break;
case 7:
printf("please enter what you shoule find out>\n");
scanf("%d",&item);
node = find(&list, item);
if(node == NULL){
printf("can not find %d\n", item);
}
break;
case 8:
printf("length is %ld\n", list.size);
break;
case 9:
printf("please enter what you want to delete>\n");
scanf("%d",&item);
delete_val(&list, item);
show_list(&list);
break;
case 10:
// sort(&list);
//show_list(&list);
break;
case 11:
sort(&list);
show_list(&list);
break;
case 12:
resver(&list);
show_list(&list);
break;
case 13:
resver(&list);
show_list(&list);
break;
case 14:
clear(&list);
show_list(&list);
break;
case 15:
destroy(&list);
break;
default:
break;
}
}
//destroy(&list);
}
