Write the code about Program for Least Recently used Algorithm in C++.Requirements are as follows:1、 Create a page access sequence (page number range 0-18) using a random function. The sequence length is 54 and assume that the number of main memory frames allocated to the thread is 6, that is, M = 6. 2、 Implement the LRU algorithm for page replacement on the above access sequence. 3、 Output the page replacement sequence and the page fault rate.4、output each page number

Sure, here's the updated code that outputs each page number:

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    const int N = 54; // length of page access sequence
    const int M = 6; // number of main memory frames
    const int P = 19; // page number range (0-18)

    // generate page access sequence randomly
    vector<int> page_seq;
    for (int i = 0; i < N; ++i) {
        int page = rand() % P;
        page_seq.push_back(page);
        cout << "Page " << page << " accessed." << endl;
    }

    // LRU algorithm
    vector<int> frames(M, -1); // initialize all frames to -1 (empty)
    vector<int> page_fault_seq; // record page faults
    int page_faults = 0;
    for (int i = 0; i < N; ++i) {
        int page = page_seq[i];
        auto it = find(frames.begin(), frames.end(), page); // check if page is already in memory
        if (it == frames.end()) { // page fault
            ++page_faults;
            if (frames[0] == -1) { // there is an empty frame
                frames[0] = page;
            } else { // no empty frame, need to evict the least recently used page
                int lru_page = frames.back(); // the last page in the frames is the LRU page
                frames.pop_back();
                frames.insert(frames.begin(), page); // insert the new page at the front
                page_fault_seq.push_back(lru_page);
            }
        } else { // page hit
            frames.erase(it);
            frames.insert(frames.begin(), page); // move the page to the front
        }

        cout << "Page " << page << " is in memory: ";
        for (auto f : frames) {
            if (f == -1) {
                cout << "- ";
            } else {
                cout << f << " ";
            }
        }
        cout << endl;
    }

    // output results
    cout << "Page replacement sequence: ";
    for (auto p : page_fault_seq) {
        cout << p << " ";
    }
    cout << endl;
    cout << "Page fault rate: " << static_cast<double>(page_faults) / N << endl;

    return 0;
}

Explanation:

- We first generate a page access sequence of length 54 using a random function. We assume that the page number range is 0-18. For each page accessed, we output a message indicating which page is accessed.
- We then implement the LRU algorithm for page replacement on the above access sequence. We use a vector `frames` to represent the main memory frames, and initialize all frames to -1 (empty). We also use a vector `page_fault_seq` to record the page replacement sequence (i.e., the pages that are evicted from memory due to page faults).
- For each page in the access sequence, we check if it is already in memory. If it is, we move it to the front of `frames` (since it is the most recently used page). If it is not, we check if there is an empty frame. If there is, we simply put the page in that frame. If there is not, we evict the least recently used page (which is the last page in `frames`), and put the new page in the front of `frames`. We also record the evicted page in `page_fault_seq`. After each page access, we output a message indicating which pages are currently in memory.
- After processing the entire access sequence, we output the page replacement sequence and the page fault rate.