cipandiaodusuanfa1.txt

包括 &#61548 先来先服务调度算法 &#61548 最短寻道优先调度算法 &#61548 扫描算法

磁盘调度算法(去年自考北大上机0S题)楼主pgood（没看过海）2002-12-03 14:02:49 在 软件培训/认证/考试 / 其他 提问
明天就要去考OS的上机了,在网上找了找以前的试题,觉得一点低也没有,全当练习了!   
  要是能把LINUX内核通读一遍,那有多好啊!都30的人了,还执迷不悟!   
  //   t1.cpp   :   Defines   the   entry   point   for   the   console   application.   
  //   
    
  #include   "stdafx.h"   
    
  /*   
  3、磁盘调度算法     
    
  要求：     
    
    1。实现三种算法：     
    
        1。先来先服务     
          
        2。最短寻道优先（老师会给当前磁头的位置）     
    
        3。电梯算法     
    
    2。磁道服务顺序从指定的文本文件（TXT文件）中取出     
    
    3。输出：     
    
      第一行：磁道的服务顺序     
    
      第二行：显示移动总道数     
    
    
  参考题目：书   P130     
    
    
  */   
  //   t1.cpp   :   定义控制台应用程序的入口点。   
  //   
    
  #include   "stdafx.h"   
  #include"math.h"   
  #include"stdlib.h"   
  #include"string.h"   
  struct   Head   
  {   
  int   nPosition;   
  bool   bVisited;   
  };   
  void   Visit(struct   Head   *pHead)   
  {   
  printf("visite   cy:%d\n",pHead->nPosition);   
  pHead->bVisited=true;   
  }   
  int   ReadInputKeyboard(struct   Head   *pHead,int   *pCurrentPosition,int   nMaxNumber)   
  {   
  int   i;   
  printf("please   input   Current   position:");   
  scanf("%d",pCurrentPosition);   
  printf("please   input   will   visit   position:");   
  for(i=0;i<nMaxNumber;i++)   
  {   
  scanf("%d",&pHead[i].nPosition);   
  pHead[i].bVisited=false;   
  if(pHead[i].nPosition<0)   
  break;   
  }   
  return   i;   
  }   
  int   ReadInputFile(struct   Head   *pHead,int   *pCurrentPosition,int   nMaxNumber)   
  {   
  int   i;   
  char   szFileName[256],*q,*p,szTemp[20];   
  printf("please   input   filename:");   
  scanf("%s",szFileName);   
    
  FILE   *pFile=fopen(szFileName,"r");   
  if(pFile==NULL)   
  {   
  printf("open   file   %s   error",szFileName);   
  return   -1;   
  }   
    
  for(i=0;!feof(pFile)   &&i<nMaxNumber;)   
  {   
  p=szFileName;   
  fgets(p,256,pFile);   
  while(q=strchr(p,','))   
  {   
  memset(szTemp,0,sizeof(szTemp)*sizeof(char));   
  strncpy(szTemp,p,q-p);   
  p=q+1;   
  if(i==0)   
  *pCurrentPosition=atoi(szTemp);   
  else   
  {   
  pHead[i-1].nPosition=atoi(szTemp);   
  pHead[i-1].bVisited=false;   
  }   
  i++;   
  }   
  memset(szTemp,0,sizeof(szTemp)*sizeof(char));   
  pHead[i-1].nPosition=atoi(p);   
  pHead[i-1].bVisited=false;   
  //i++;   
    
    
  }   
  fclose(pFile);   
  return   i;   
  }   
    
  int   FifoVisit(int   nCurrentPosition,struct   Head   *pHead,int   nNumber)   
  {   
  //先来先服务   
  int   nHaveVisited=0;   
  int   nMoveDistance=0;   
  int   i;   
  while(nHaveVisited<nNumber)   
  {   
  for(i=0;i<nNumber;i++)   
  {   
  if(pHead[i].bVisited)   
  continue;   
  Visit(&pHead[i]);   
  nHaveVisited++;   
  nMoveDistance+=abs(nCurrentPosition-pHead[i].nPosition);   
  nCurrentPosition=pHead[i].nPosition;   
  }   
  }   
  printf("the   sum   of   move   distance:%d\n",nMoveDistance);   
  return   nMoveDistance;   
  }   
    
    
  int   SsfoVisit(int   nCurrentPosition,struct   Head   *pHead,int   nNumber)   
  {   
  //   最短寻找时间优先   
  int   nHaveVisited=0;   
  int   nMoveDistance=0;   
  int   nMinDistance=0;   
  int   nMinIndex=0;   
  int   i;   
  while(nHaveVisited<nNumber)   
  {   
  nMinDistance=0xffff;   
  nMinIndex=0;   
  //找最小值   
  for(i=0;i<nNumber;i++)   
  {   
  if(pHead[i].bVisited)   
  continue;   
  if(nMinDistance>abs(pHead[i].nPosition-nCurrentPosition))   
  {   
  nMinDistance=abs(pHead[i].nPosition-nCurrentPosition);   
  nMinIndex=i;   
  }   
  }   
  //访问   
  Visit(&pHead[nMinIndex]);   
  nHaveVisited++;   
  nMoveDistance+=nMinDistance;   
  nCurrentPosition=pHead[nMinIndex].nPosition;   
  }   
  printf("the   sum   of   move   distance:%d\n",nMoveDistance);   
  return   nMoveDistance;   
  }   
  int   DtVisit(int   nCurrentPosition,bool   bOut,struct   Head   *pHead,int   nNumber)   
  {   
  //电梯调度算法   
  int   nHaveVisited=0;   
  int   nMoveDistance=0;   
  int   nMinDistance=0;   
  int   nMinIndex=0;   
  int   i;   
  while(nHaveVisited<nNumber)   
  {   
  nMinDistance=0xffff;   
  nMinIndex=0;   
  //找最小值   
  for(i=0;i<nNumber;i++)   
  {   
  if(pHead[i].bVisited)   
  continue;   
  if(bOut   &&   pHead[i].nPosition<nCurrentPosition   ||   
  !bOut   &&   pHead[i].nPosition>nCurrentPosition)   
  {   
  if(nMinDistance>abs(pHead[i].nPosition-nCurrentPosition))   
  {   
  nMinDistance=abs(pHead[i].nPosition-nCurrentPosition);   
  nMinIndex=i;   
  }   
  }   
    
  }   
  if(nMinDistance==0xffff)   
  {   
  bOut=!bOut;   
  continue;   
  }   
    
  //访问   
  Visit(&pHead[nMinIndex]);   
  nHaveVisited++;   
  nMoveDistance+=nMinDistance;   
  nCurrentPosition=pHead[nMinIndex].nPosition;   
  }   
  printf("the   sum   of   move   distance:%d\n",nMoveDistance);   
  return   nMoveDistance;   
  }   
  int   DxVisit(int   nCurrentPosition,struct   Head   *pHead,int   nNumber)   
  {   
  //单向调度算法   
  int   nHaveVisited=0;   
  int   nMoveDistance=0;   
  int   nMinDistance=0;   
  int   nMinIndex=0;   
  int   i;   
  while(nHaveVisited<nNumber)   
  {   
  nMinDistance=0xffff;   
  nMinIndex=0;   
  //找最小值   
  for(i=0;i<nNumber;i++)   
  {   
  if(pHead[i].bVisited)   
  continue;   
  if(pHead[i].nPosition>nCurrentPosition   )   
  {   
  if(nMinDistance>abs(pHead[i].nPosition-nCurrentPosition))   
  {   
  nMinDistance=abs(pHead[i].nPosition-nCurrentPosition);   
  nMinIndex=i;   
  }   
  }   
    
  }   
  if(nMinDistance==0xffff)   
  {   
  nMoveDistance+=199-nCurrentPosition;   
  nCurrentPosition=0;   
  continue;   
  }   
    
  //访问   
  Visit(&pHead[nMinIndex]);   
  nHaveVisited++;   
  nMoveDistance+=nMinDistance;   
  nCurrentPosition=pHead[nMinIndex].nPosition;   
  }   
  printf("the   sum   of   move   distance:%d\n",nMoveDistance);   
  return   nMoveDistance;   
  }   
  int   main(int   argc,   char*   argv[])   
  {   
  //p114   
  struct   Head   mylist[20];//={98,false,183,false,37,false,122,false,14,false,124,false,65,false,67,false};   
  //int   nCurrentPosition=53;   
  //int   nRealNumber=8;   
    
  int   nCurrentPosition=0;   
  int   nRealNumber=ReadInputFile(mylist,&nCurrentPosition,20);   
  // FifoVisit(nCurrentPosition,mylist,nRealNumber);   
  // SsfoVisit(nCurrentPosition,mylist,nRealNumber);   
  //DtVisit(nCurrentPosition,false,mylist,nRealNumber);   
  DxVisit(nCurrentPosition,mylist,nRealNumber);   
    
  return   0;   
  }