操作系统实验LRU算法

Question

初学编程
操作系统LRU算法c++实现
private处报错

#include<iostream>
#include<list>
#include<stdlib.h>
#include<time.h>
using namespace std;

class LRU{
    public:
        LRU(){data=1;used=0;time=0;}
        LRU(int d,int u,int t){
            data = d;used = u;time = t;
        }
        
        void be_used();
         
        friend class List;
        
//    private:        
        int used;
        int data;
        int time;
};

void LRU::be_used(){
    used++;    
}

bool comp_used(LRU& p1,LRU& p2){
    if(p1.used == p2.used){
        return (p1.time < p2.time);
    }else {
        return (p1.used < p2.used);    
    }
}

class List{
    public:
        int lru(LRU& p,int num){
            int interrupt_LRU = 1;
//            cout<<p.data<<" "<<p.used<<endl;
            for(list<LRU>::iterator it = l.begin();it!=l.end();++it){
                if((*it).data == p.data){
//                    cout<<"no interrupt_LRU"<<endl;
                    it->be_used();
                    interrupt_LRU = 0;
                }
            }            
            
            if(interrupt_LRU){
//                cout<<"interrupt_LRU"<<endl;
                if(l.size()<num){
                    l.push_back(p);
                //    cout<<(*l.begin()).data;
                }else {
                    l.pop_front();
                    l.push_front(p);
                }
            }
            
            for(list<LRU>::iterator it = l.begin();it!=l.end();++it){
                (*it).time++;
            }
            l.sort(comp_used);
/*        
            for(list<LRU>::iterator it = l.begin();it!=l.end();++it){
                cout<<(*it).data<<" ";
            }
            cout<<endl;
            cout<<endl;
*/        
            return interrupt_LRU;
        }
    private:
        list<LRU> l;
};

int main(){
    int num = 0;
     int x = 0;
     
    cout<<"输入页框数：";
     cin>>num;
     cout<<endl;
    
    cout<<"输入访问页面序列长度：";
    cin>>x;
    cout<<endl;

    List l;
    int con_LRU = x;
    int fail_LRU = 0;
    
    while(con_LRU){
        int a=rand()%9+1;
//        cout<<"新页:"<<a<<endl;
        LRU page(a,1,0);
//        cout<<page.data<<" "<<page.used<<endl;
            
        if(l.lru(page,num)){
            fail_LRU++;
        }
        
        con_LRU--;
    }
    cout<<"LRU缺页中断率："<<fail_LRU*100/x<<"%"<<endl;
    return 0;
}

Answer 1

报错是因为 comp_used 函数访问了 private 关键字保护的属性。

其实你已经使用了一个 friend，为何不再来一个？

#include<iostream>
#include<list>
#include<stdlib.h>
#include<time.h>
using namespace std;
 
class LRU{
    public:
        LRU(){data=1;used=0;time=0;}
        LRU(int d,int u,int t){
            data = d;used = u;time = t;
        }
        
        void be_used();
         
        friend class List;
        friend bool comp_used(LRU&, LRU&); // 声明 friend 函数
        
   private:        
        int used;
        int data;
        int time;
};
 
void LRU::be_used(){
    used++;    
}
 
bool comp_used(LRU& p1,LRU& p2){
    if(p1.used == p2.used){
        return (p1.time < p2.time);
    }else {
        return (p1.used < p2.used);    
    }
}
 
class List{
    public:
        int lru(LRU& p,int num){
            int interrupt_LRU = 1;
//            cout<<p.data<<" "<<p.used<<endl;
            for(list<LRU>::iterator it = l.begin();it!=l.end();++it){
                if((*it).data == p.data){
//                    cout<<"no interrupt_LRU"<<endl;
                    it->be_used();
                    interrupt_LRU = 0;
                }
            }            
            
            if(interrupt_LRU){
//                cout<<"interrupt_LRU"<<endl;
                if(l.size()<num){
                    l.push_back(p);
                //    cout<<(*l.begin()).data;
                }else {
                    l.pop_front();
                    l.push_front(p);
                }
            }
            
            for(list<LRU>::iterator it = l.begin();it!=l.end();++it){
                (*it).time++;
            }
            l.sort(comp_used);
/*        
            for(list<LRU>::iterator it = l.begin();it!=l.end();++it){
                cout<<(*it).data<<" ";
            }
            cout<<endl;
            cout<<endl;
*/        
            return interrupt_LRU;
        }
    private:
        list<LRU> l;
};
 
int main(){
    int num = 0;
     int x = 0;
     
    cout<<"输入页框数：";
     cin>>num;
     cout<<endl;
    
    cout<<"输入访问页面序列长度：";
    cin>>x;
    cout<<endl;
 
    List l;
    int con_LRU = x;
    int fail_LRU = 0;
    
    while(con_LRU){
        int a=rand()%9+1;
//        cout<<"新页:"<<a<<endl;
        LRU page(a,1,0);
//        cout<<page.data<<" "<<page.used<<endl;
            
        if(l.lru(page,num)){
            fail_LRU++;
        }
        
        con_LRU--;
    }
    cout<<"LRU缺页中断率："<<fail_LRU*100/x<<"%"<<endl;
    return 0;
}

这样是可以通过编译的。

Answer 2

谢谢回答，我去试了一下，dev-c++还是报错了，但是换visual studio编译通过。是不是我dev-c++的问题