银行家.cpp

操作系统 银行家算法 。。。。及课件 和课后习题答案

// 银行家.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream.h>

#define M 5     //总进程数
#define N 3     //总资源数
#define FALSE 0
#define TRUE 1
int MAX[M][N]={{7,5,3},{3,2,2},{9,0,2},{2,2,2},{4,3,3}};//M个进程对N类资源最大资源需求量
int ALLOCATION[M][N]={{0,1,0},{2,0,0},{3,0,2},{2,1,1},{0,0,2}};//M个进程已经得到N类资源的资源量
int NEED[M][N]={{7,4,3},{1,2,2},{6,0,0},{0,1,1},{4,3,1}};//M个进程还需要N类资源的资源量
int AVAILABLE[N]={3,3,2};//系统可用资源数 
int Request[N]={0,0,0};
int proc[M]={0,1,2,3,4};
void show();
void safe(int);
void main()
{
	int i=0;int j=0;
	char flag='Y';
	show(); 
	while(flag=='Y'||flag=='y')
	{
	cout<<"请输入需要请求资源的进程号：";
	cin>>i;
	if (i<0||i>4) cout<<"输入的进程号不存在，请重新输入!"<<endl;
	cout<<"请输入此进程需要申请的资源数："<<endl;
	for(j=0;j<3;j++)
		{
			cout<<"资源"<<j<<":";
			cin>>Request[j];
			if(Request[j]>NEED[i][j])
			{
				cout<<"进程"<<i<<"申请的资源数大于此进程所需第"<<j<<"类资源的资源量!";
				cout<<"申请不合理,请重新选择!"<<endl<<endl;
				flag='Y';
				break;
			}
		   if(Request[j]>AVAILABLE[j])
		   {
			   cout<<"进程"<<i<<"申请的资源数大于第"<<" "<<j<<" "<<"类资源可利用的资源量!";
				cout<<"申请不合理,请重新选择!"<<endl<<endl;
				flag='Y';
				break;
			}
		}
	if(Request[j]<NEED[i][j] && Request[j]<AVAILABLE[j])	continue; 
				safe(i);  
				cout<<endl;
				cout<<"是否继续银行家算法演示，按'Y'或'y'键继续,按'N'或'n'键退出演示:";
				cin>>flag;
	}
}
void show()//显示已知
{
	cout<<"       "<<"MAX"<<"   "<<"ALLOCATION"<<"    "<<"NEED"<<endl;
	for(int i=0;i<5;i++)
	{
		cout<<proc[i]<<"     "<<MAX[i][0]<<' '<<MAX[i][1]<<' '<<MAX[i][2]<<"     ";
		cout<<ALLOCATION[i][0]<<' '<<ALLOCATION[i][1]<<' '<<ALLOCATION[i][2]<<"     ";
        cout<<NEED[i][0]<<' '<<NEED[i][1]<<' '<<NEED[i][2]<<endl;

	}
	cout<<"AVAILABLE:"<<"  "<<AVAILABLE[0]<<" "<<AVAILABLE[1]<<" "<<AVAILABLE[2]<<endl;
};
void safe(int s)//安全检查
{
int WORK[N],FINISH[M],temp[M];
int i,j,k=0,count;
for(i=0;i<M;i++) FINISH[i]=FALSE;
for(j=0;j<N;j++)  WORK[j]=AVAILABLE[j];
i=s;
while (i<M)
 {  
	 if(FINISH[i]==FALSE)
	{
	  count=0;
	   for(j=0;j<N;j++)
	   {
	    if( NEED[i][j]>WORK[j])   count+=1;
		else WORK[j]=WORK[j]+ALLOCATION[i][j];
	   }
	if(count==0)  
	{
		FINISH[i]=TRUE;
        temp[k]=i;
		k++;
		i=0;
	}
	else {
			for(j=0;j<N;j++)  {if( NEED[i][j]<=WORK[j])  WORK[j]=WORK[j]-ALLOCATION[i][j];}
			i++;}
	}
	else i++;
					 
				   
 }
	count=0;
	for(i=0;i<M;i++)
	   if(FINISH[i]==FALSE)  count+=1;
	   if( count!=0)
		{
			cout<<endl;
			cout<<"系统不安全!!!本次资源申请不成功!!!"<<endl;
			cout<<endl;
			}
				   
		else{
		        cout<<endl;
				cout<<"经安全性检验，系统安全，本次分配成功."<<endl;
				cout<<endl;
				cout<<" 本次安全序列:";
				for(i=0;i<M;i++)cout<<"进程"<<temp[i]<<"->";
				cout<<endl;}
                 
};