运用C++编程序实现先进先出算法（FIFO）、最近最久未使用算法（LRU）算法、最佳置换算法（OPT）、时钟置换算法的具体实现过程，并计算访问命中率。

以下是C++实现四种页面置换算法的示例代码：

FIFO算法：

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

int main()
{
    int n, m;
    queue<int> q;
    int page[100];   //存储页面号
    int hit = 0;     //命中次数
    double rate;     //命中率

    cout << "请输入页面数：";
    cin >> n;
    cout << "请输入页面序列：";
    for (int i = 0; i < n; i++)
    {
        cin >> page[i];
    }
    cout << "请输入内存块数：";
    cin >> m;

    for (int i = 0; i < n; i++)
    {
        if (q.size() < m)  //内存块未满
        {
            q.push(page[i]);
        }
        else   //内存块已满
        {
            int flag = 0;
            int temp = q.front();
            q.pop();
            for (int j = 0; j < q.size(); j++)
            {
                if (page[i] == temp)
                {
                    hit++;
                    flag = 1;
                    break;
                }
                temp = q.front();
                q.pop();
                q.push(temp);
            }
            if (flag == 0)
            {
                q.push(page[i]);
            }
        }
    }

    rate = 1.0 * hit / n;
    cout << "命中率：" << rate << endl;

    return 0;
}

LRU算法：

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

int main()
{
    int n, m;
    list<int> l;
    int page[100];  //存储页面号
    int hit = 0;    //命中次数
    double rate;    //命中率

    cout << "请输入页面数：";
    cin >> n;
    cout << "请输入页面序列：";
    for (int i = 0; i < n; i++)
    {
        cin >> page[i];
    }
    cout << "请输入内存块数：";
    cin >> m;

    for (int i = 0; i < n; i++)
    {
        if (l.size() < m)  //内存块未满
        {
            l.push_back(page[i]);
        }
        else   //内存块已满
        {
            int flag = 0;
            for (list<int>::iterator it = l.begin(); it != l.end(); it++)
            {
                if (page[i] == *it)
                {
                    hit++;
                    flag = 1;
                    l.erase(it);
                    l.push_back(page[i]);
                    break;
                }
            }
            if (flag == 0)
            {
                l.pop_front();
                l.push_back(page[i]);
            }
        }
    }

    rate = 1.0 * hit / n;
    cout << "命中率：" << rate << endl;

    return 0;
}

OPT算法：

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

int main()
{
    int n, m;
    int page[100];      //存储页面号
    int mem[100];       //存储内存块的页面号
    int next[100];      //存储下一个使用该页面号的位置
    int hit = 0;        //命中次数
    double rate;        //命中率

    cout << "请输入页面数：";
    cin >> n;
    cout << "请输入页面序列：";
    for (int i = 0; i < n; i++)
    {
        cin >> page[i];
    }
    cout << "请输入内存块数：";
    cin >> m;
    cout << "请输入内存块内容：";
    for (int i = 0; i < m; i++)
    {
        cin >> mem[i];
    }

    for (int i = 0; i < m; i++)   //初始化next数组
    {
        int j;
        for (j = n - 1; j >= 0; j--)
        {
            if (mem[i] == page[j])
            {
                next[i] = j;
                break;
            }
        }
        if (j < 0)
        {
            next[i] = n;
        }
    }

    for (int i = m; i < n; i++)
    {
        int flag = 0;
        int k = 0;
        for (int j = 0; j < m; j++)
        {
            if (page[i] == mem[j])
            {
                hit++;
                flag = 1;
                break;
            }
            if (next[j] > next[k])
            {
                k = j;
            }
        }
        if (flag == 0)
        {
            mem[k] = page[i];
            next[k] = n;
            for (int j = i + 1; j < n; j++)
            {
                if (page[j] == mem[k])
                {
                    next[k] = j;
                    break;
                }
            }
        }
    }

    rate = 1.0 * hit / n;
    cout << "命中率：" << rate << endl;

    return 0;
}

时钟置换算法：

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

int main()
{
    int n, m;
    queue<int> q;
    int page[100];     //存储页面号
    int ref[100];      //存储页面的访问位
    int hit = 0;       //命中次数
    double rate;       //命中率

    cout << "请输入页面数：";
    cin >> n;
    cout << "请输入页面序列：";
    for (int i = 0; i < n; i++)
    {
        cin >> page[i];
    }
    cout << "请输入内存块数：";
    cin >> m;

    for (int i = 0; i < m; i++)   //初始化ref数组
    {
        ref[i] = 0;
    }

    for (int i = 0; i < n; i++)
    {
        if (q.size() < m)  //内存块未满
        {
            int flag = 0;
            for (int j = 0; j < q.size(); j++)
            {
                if (page[i] == q.front())
                {
                    hit++;
                    flag = 1;
                    ref[j] = 1;
                    break;
                }
                int temp = q.front();
                q.pop();
                q.push(temp);
            }
            if (flag == 0)
            {
                q.push(page[i]);
            }
        }
        else   //内存块已满
        {
            int flag = 0;
            while (flag == 0)
            {
                if (ref[0] == 0)
                {
                    q.pop();
                    q.push(page[i]);
                    flag = 1;
                }
                else
                {
                    ref[0] = 0;
                    int temp = q.front();
                    q.pop();
                    q.push(temp);
                }
            }

            for (int j = 0; j < q.size(); j++)
            {
                if (page[i] == q.front())
                {
                    hit++;
                    ref[j] = 1;
                    break;
                }
                int temp = q.front();
                q.pop();
                q.push(temp);
            }
        }
    }

    rate = 1.0 * hit / n;
    cout << "命中率：" << rate << endl;

    return 0;
}