c/c++ 线性表之双向链表

c/c++ 线性表之双向链表

线性表之双向链表

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是NULL。

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

shuangnode.h

#ifndef __SHUANGNODE__
#define __SHUANGNODE__

#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

shuangnode.c

#include "shuangnode.h"

void init(NodeList* list){
  list->first = (Node*)malloc(sizeof(Node));
  list->last = list->first;
  list->last->next = NULL;
  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 = NULL;
  
  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;
  p->next = list->first->next;
  //第一次添加节点的时候要移动未指针
  if(NULL == list->first->next){
    list->last = 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{
    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 != NULL){
    printf("%d->", tmp->data);
    tmp = tmp->next;
  }
  printf("NULL
");
}

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 = NULL;
  //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。因为list->first->next已经为NULL，下面的list->first->next->before就会在执行时候崩掉，所以要return掉
  if(list->first->next == list->last){
    list->last = list->first;
    list->last->next = NULL;
    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 != NULL && val > p->next->data){
    p = p->next;
  }
  //第一次加节点，或者，最后一个节点也没有给的值大的时候
  if(NULL == p->next){
    n->next = NULL;
    n->before = list->last;
    list->last->next = 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 != NULL && p->next->data != val){
    p = p->next;
  }
  if(NULL == p->next){
    return NULL;
  }
  printf("%d is found
", p->next->data);
  return p->next;
}
//寻找给定值的节点的前一个节点的位置
Node* find1(NodeList* list, ElemType val){
  if(list->size == 0)return NULL;

  Node* p = list->first;
  while(p->next != NULL && p->next->data != val){
    p = p->next;
  }
  if(NULL == p->next){
    return NULL;
  }
  printf("%d is found
", p->next->data);
  return p;
}
void delete_val(NodeList* list, ElemType val){
  Node* p = find1(list, val);
  if(NULL == p) return;

  free(p->next);
  //删除的节点是尾节点的时候，要移动last
  if(p->next == list->last){
    list->last = p;
    p->next = NULL;
    list->size--;
    return;
  }

  p->next->next->before = p;
  p->next = p->next->next;

  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 = NULL;
  
  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 != NULL && p->data > t->next->data){
      t = t->next;
    }
    //ｔ为first，或者t为last,都是尾插
    if(t->next == NULL){
      t->next = p;
      p->next = NULL;
      p->before = t;
      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 = NULL;

  Node* tmp;
  while(second != NULL){
    //必须保存second的next，因为下面的代码，会改变second的next
    tmp = second->next;
    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 != NULL){
    free(p);
    p = p->next;
  }
  list->last = list->first;
  list->last->next = NULL;
  list->size = 0;
}

void destroy(NodeList* list){
  Node* p = list->first;
  while(p != NULL){
    free(p);
    p = p->next;
  }
  list->size = 0;  
}

shuangnodemain.c

#include "shuangnode.h"

int main(){
  NodeList list;
  init(&list);
  int select = 1;
  ElemType item;
  Node* node = NULL;
  while(select){
    printf("*****************************************
");
    printf("*** [1]   push_back   [2]  push_front ***
");
    printf("*** [3]   show_list   [4]  pop_back   ***
");
    printf("*** [5]   pop_front   [6]  insert_val ***
");
    printf("*** [7]   find        [8]  length     ***
");
    printf("*** [9]   delete_val  [10] sort       ***
");
    printf("*** [11]  sort        [12] resver     ***
");
    printf("*** [13]              [14] clear      ***
");
    printf("*** [0]   quit        [15*]destroy    ***
");
    printf("*****************************************
");
    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>
");
      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>
");
      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>
");
      scanf("%d",&item);
      insert_val(&list, item);
      show_list(&list);
      break;
    case 7:
      printf("please enter what you shoule find out>
");
      scanf("%d",&item);
      node = find(&list, item);
      if(node == NULL){
	printf("can not find %d
", item);
      }
      break;
    case 8:
      printf("length is %ld
", list.size);
      break;
    case 9:
      printf("please enter what you want to delete>
");
      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);
}