#include<stdio.h>
#include<stdlib.h>

typedef struct
{
  int data;          //資料項
  int time;      //記錄進入的時間,計算頁面調入物理塊的時間，然後比較，讓最時間最久的置換出去
} Page;             //頁面定義

int max(int a,int b,int c)
{
  if(a<b) a=b;
  if(a<c) a=c;
  return a; 
}

int main()
{
  Page Physical_block[3];
  int page_num[]={7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1};

  printf("-----Least Recently Used-----\n");
  printf("Reference chars initialized as follow:\n");
  printf("7 0 1 2 0 3 0 4 2 3 0 3 2 1 2 0 1 7 0 1\n");

  for(int i=0;i<3;i++)           //物理塊陣列的初始化
  {
    Physical_block[i].data=page_num[i];
    Physical_block[i].time=0;
   
    if(i==1)
      Physical_block[i-1].time++; 
    if(i==2)
    {
      Physical_block[i-1].time++; 
      Physical_block[i-2].time++;  
    } 
  }
 
  printf("Display the replacement procedure:\n");
  printf("---------------------------------- \n");
 
  for(int loop=3;loop<20;loop++)       //替換並輸出
  {
   //如果不缺頁，不置換
   if(!(Physical_block[0].data==page_num[loop] ||
        Physical_block[1].data==page_num[loop] ||
        Physical_block[2].data==page_num[loop]))
    {
       int c1=Physical_block[0].time; 
       int c2=Physical_block[1].time;
       int c3=Physical_block[2].time;
   
       if(max(c1,c2,c3)==c1)
       {
         Physical_block[0].data=page_num[loop];
         Physical_block[0].time=0; 
         Physical_block[1].time++; 
         Physical_block[2].time++;   
       }
       else if(max(c1,c2,c3)==c2)
       {
         Physical_block[1].data=page_num[loop];
         Physical_block[1].time=0;
         Physical_block[0].time++; 
         Physical_block[2].time++;   
       }
       else if(max(c1,c2,c3)==c3)
       {
         Physical_block[2].data=page_num[loop];
         Physical_block[2].time=0; 
         Physical_block[0].time++; 
         Physical_block[1].time++;     
       } 
    }
    //不置換，但要計數
    if(Physical_block[0].data==page_num[loop])  
    {
      Physical_block[0].time=0; 
      Physical_block[1].time++; 
      Physical_block[2].time++; 
    }
   
    if(Physical_block[1].data==page_num[loop])
    {
      Physical_block[1].time=0;
      Physical_block[0].time++; 
      Physical_block[2].time++; 
    }
   
    if(Physical_block[2].data==page_num[loop])
    {
      Physical_block[2].time=0;
      Physical_block[0].time++; 
      Physical_block[1].time++; 
    } 
    printf("%d.Physical block array content:",(loop-2));
    for(int inloop=0;inloop<3;inloop++)                
        printf("%d\t",Physical_block[inloop].data);
       printf("\n");
  }
 
  return 0; 
}