#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
typedef int status;
typedef int elemtype;
typedef struct node{
  elemtype data;
  int freq;
  struct node * next;
  struct node * prior;
}node;
typedef struct node* dlinklist;

status visit(elemtype c){
  printf("%d ",c);
}

/*雙向鏈表初始化*/
status initdlinklist(dlinklist * head,dlinklist * tail){
  (*head)=(dlinklist)malloc(sizeof(node));
  (*tail)=(dlinklist)malloc(sizeof(node));
  if(!(*head)||!(*tail))
    return ERROR;
  /*這一步很關鍵*/ 
  (*head)->prior=NULL;
  (*tail)->next=NULL;
  (*head)->freq=0;
  (*tail)->freq=0; 
  /*鏈表為空時讓頭指向尾*/
  (*head)->next=(*tail);
  (*tail)->prior=(*head);
}

/*判定是否為空*/
status emptylinklist(dlinklist head,dlinklist tail){
  if(head->next==tail)
    return TRUE;
  else
    return FALSE;
} 

/*尾插法創建鏈表*/ 
status createdlinklist(dlinklist head,dlinklist tail,elemtype data){
  dlinklist pmove=head,qmove=tail,pinsert;
  pinsert=(dlinklist)malloc(sizeof(node));
  if(!pinsert)
    return ERROR;
  else{
    pinsert->data=data;
    pinsert->prior=pmove;
    pinsert->next=pmove->next;
    pmove->next->prior=pinsert;
    pmove->next=pinsert;
  }
}

/*正序打印鏈表*/ 
status traverselist(dlinklist head,dlinklist tail){
  dlinklist pmove=head->next;
  while(pmove!=tail){
    visit(pmove->data);
    pmove=pmove->next;
  }
  printf("\n");
}

status traverselist2(dlinklist head,dlinklist tail){
  dlinklist pmove=head->next;
  while(pmove!=tail){
    visit(pmove->freq);
    pmove=pmove->next;
  }
  printf("\n");
}

/*在鏈表頭插入元素*/
status inserthead(dlinklist head,dlinklist tail,elemtype data){
  dlinklist pinsert;
  pinsert=(dlinklist)malloc(sizeof(node));
  pinsert->data=data;
  pinsert->next=NULL;
  pinsert->prior=NULL;
  tail->prior->next=pinsert;
  pinsert->prior=tail->prior;
  pinsert->next=tail;
  tail->prior=pinsert;
  return OK;
}

/*按使用頻次排序*/ 
status locateorder(dlinklist head,dlinklist tail,elemtype data){
  dlinklist pmove=head->next,qmove;
  while(pmove!=tail&&pmove->data!=data)
    pmove=pmove->next;
  if(pmove==tail){
    printf("未找到\n");
    return ERROR;
  }
  else{
    pmove->freq++;
    qmove=pmove->prior;
    while(qmove!=head&&qmove->freq<pmove->freq)//向前尋找比pmove->freq大的qmove->freq
       qmove=qmove->prior;
    if(qmove->next!=pmove){//如果找到的qmove和pmove不是直接的前驅后繼關系
      pmove->next->prior=pmove->prior;
      pmove->prior->next=pmove->next;//將pmove取下
      pmove->prior=qmove;
      pmove->next=qmove->next;
      qmove->next->prior=pmove;
      qmove->next=pmove;//插到qmove之后
    }
  }
}

int main(void){
  dlinklist head,tail,pmove=head;
  int i=0;
  initdlinklist(&head,&tail);
  for(i=0;i<10;i++)
    inserthead(head,tail,i);
  printf("未經過排序的鏈表為\n");
  traverselist(head,tail);
  printf("在按使用頻率排序后的鏈表為:\n"); 
  locateorder(head,tail,5);
  for(int i=0;i<3;i++){
    locateorder(head,tail,6);
  }
  traverselist(head,tail);
  printf("各元素使用頻率為\n");
  traverselist2(head,tail);
}