页面置换算法的三种方法的c++代码

页面置换算法是操作系统中用于管理内存的一种重要算法，常见的有三种方法：先进先出（FIFO）、最近最少使用（LRU）和时钟（Clock）算法。

以下是这三种算法的 C++ 代码实现：

1. 先进先出（FIFO）算法：

#include <iostream>
#include <queue>
using namespace std;

int main()
{
    int page_faults = 0, n, m, page;
    queue<int> q;

    cout << "Enter the number of frames: ";
    cin >> n;

    int frames[n];

    cout << "Enter the number of pages: ";
    cin >> m;

    cout << "Enter the page reference string: ";
    for(int i = 0; i < m; i++) {
        cin >> page;

        if(q.size() < n && find(frames, frames + n, page) == frames + n) {
            q.push(page);
            frames[q.size() - 1] = page;
            page_faults++;
        } else if(q.size() == n && find(frames, frames + n, page) == frames + n) {
            int p = q.front();
            q.pop();
            for(int j = 0; j < n; j++) {
                if(frames[j] == p) {
                    frames[j] = page;
                    break;
                }
            }
            q.push(page);
            page_faults++;
        }
    }

    cout << "Number of page faults: " << page_faults << endl;

    return 0;
}

2. 最近最少使用（LRU）算法：

#include <iostream>
#include <list>
using namespace std;

int main()
{
    int page_faults = 0, n, m, page;
    list<int> l;

    cout << "Enter the number of frames: ";
    cin >> n;

    int frames[n];

    cout << "Enter the number of pages: ";
    cin >> m;

    cout << "Enter the page reference string: ";
    for(int i = 0; i < m; i++) {
        cin >> page;

        if(l.size() < n && find(frames, frames + n, page) == frames + n) {
            l.push_back(page);
            frames[l.size() - 1] = page;
            page_faults++;
        } else if(l.size() == n && find(frames, frames + n, page) == frames + n) {
            int p = l.front();
            l.pop_front();
            for(int j = 0; j < n; j++) {
                if(frames[j] == p) {
                    frames[j] = page;
                    break;
                }
            }
            l.push_back(page);
            page_faults++;
        } else if(find(frames, frames + n, page) != frames + n) {
            for(list<int>::iterator it = l.begin(); it != l.end(); it++) {
                if(*it == page) {
                    l.erase(it);
                    break;
                }
            }
            l.push_back(page);
        }
    }

    cout << "Number of page faults: " << page_faults << endl;

    return 0;
}

3. 时钟（Clock）算法：

#include <iostream>
using namespace std;

int main()
{
    int page_faults = 0, n, m, page, index = 0;
    bool found = false;

    cout << "Enter the number of frames: ";
    cin >> n;

    int frames[n], refbit[n];

    for(int i = 0; i < n; i++) {
        frames[i] = -1;
        refbit[i] = 0;
    }

    cout << "Enter the number of pages: ";
    cin >> m;

    cout << "Enter the page reference string: ";
    for(int i = 0; i < m; i++) {
        cin >> page;

        found = false;

        for(int j = 0; j < n; j++) {
            if(frames[j] == page) {
                found = true;
                refbit[j] = 1;
                break;
            }
        }

        if(!found) {
            while(!found) {
                if(refbit[index] == 0) {
                    frames[index] = page;
                    refbit[index] = 1;
                    index = (index + 1) % n;
                    found = true;
                } else {
                    refbit[index] = 0;
                    index = (index + 1) % n;
                }
            }
            page_faults++;
        }
    }

    cout << "Number of page faults: " << page_faults << endl;

    return 0;
}