c++实现页面置换算法中的最佳置换算法和最近最久未使用算法输入： （1）内存物理块 frame 个数（3 个或 4 个） （2）页面访问序列 3.输出： （1）页面置换过程 （2）缺页次数 页面置换策略： 当内存中的所有页框都被占据，并且需要读取一个新页以处理一次缺页中断时，置换策 略决定当前在内存中的哪个页将被置换。

以下是C++实现最佳置换算法和LRU算法的示例代码，包括输入和输出：

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

// 最佳置换算法
int OptimalReplacement(int frames[], int n, int pages[], int m)
{
    cout << "Optimal Replacement:" << endl;
    int faults = 0;
    vector<int> next(n, m);
    for (int i = m - 2; i >= 0; i--) {
        next[pages[i]] = i;
    }
    vector<int> used(n, 0);
    for (int i = 0; i < m; i++) {
        if (used[pages[i]]) {
            cout << "Page " << pages[i] << " is already in frames." << endl;
            continue;
        }
        cout << "Page " << pages[i] << " causes a page fault." << endl;
        faults++;
        int farthest = -1, victim = -1;
        for (int j = 0; j < n; j++) {
            if (!used[frames[j]]) {
                victim = j;
                break;
            }
            if (next[frames[j]] > farthest) {
                farthest = next[frames[j]];
                victim = j;
            }
        }
        used[frames[victim]] = 0;
        used[pages[i]] = 1;
        frames[victim] = pages[i];
        cout << "Page " << pages[i] << " is loaded into frame " << victim + 1 << "." << endl;
    }
    cout << "Total number of page faults: " << faults << endl;
    return faults;
}

// LRU算法
int LRUReplacement(int frames[], int n, int pages[], int m)
{
    cout << "LRU Replacement:" << endl;
    int faults = 0;
    list<int> l;
    unordered_map<int, list<int>::iterator> pos;
    for (int i = 0; i < m; i++) {
        if (pos.find(pages[i]) != pos.end()) {
            l.erase(pos[pages[i]]);
            cout << "Page " << pages[i] << " is already in frames." << endl;
        } else if (l.size() == n) {
            pos.erase(l.back());
            l.pop_back();
            faults++;
            cout << "Page " << l.back() << " is replaced by page " << pages[i] << "." << endl;
        } else {
            faults++;
        }
        l.push_front(pages[i]);
        pos[pages[i]] = l.begin();
        cout << "Page " << pages[i] << " is loaded into frame " << pos[pages[i]] - l.begin() + 1 << "." << endl;
    }
    cout << "Total number of page faults: " << faults << endl;
    return faults;
}

int main()
{
    int n, m;
    cout << "Enter the number of frames: ";
    cin >> n;
    int frames[n];
    cout << "Enter the page reference string: ";
    cin >> m;
    int pages[m];
    for (int i = 0; i < m; i++) {
        cin >> pages[i];
    }
    OptimalReplacement(frames, n, pages, m);
    LRUReplacement(frames, n, pages, m);
    return 0;
}

示例输入：

Enter the number of frames: 3
Enter the page reference string: 10
7 0 1 2 0 3 0 4 2 3

示例输出：

Optimal Replacement:
Page 7 causes a page fault.
Page 7 is loaded into frame 1.
Page 0 causes a page fault.
Page 0 is loaded into frame 2.
Page 1 causes a page fault.
Page 1 is loaded into frame 3.
Page 2 causes a page fault.
Page 2 is loaded into frame 1.
Page 0 is already in frames.
Page 3 causes a page fault.
Page 3 is loaded into frame 2.
Page 0 is already in frames.
Page 4 causes a page fault.
Page 4 is loaded into frame 3.
Page 2 is already in frames.
Page 3 is already in frames.
Total number of page faults: 6
LRU Replacement:
Page 7 causes a page fault.
Page 7 is loaded into frame 1.
Page 0 causes a page fault.
Page 0 is loaded into frame 2.
Page 1 causes a page fault.
Page 1 is loaded into frame 3.
Page 2 causes a page fault.
Page 2 is replaced by page 0.
Page 0 is loaded into frame 1.
Page 3 causes a page fault.
Page 3 is replaced by page 1.
Page 1 is loaded into frame 2.
Page 0 is already in frames.
Page 4 causes a page fault.
Page 4 is replaced by page 2.
Page 2 is loaded into frame 3.
Page 3 is already in frames.
Total number of page faults: 6