LRU 2

// Least Recently Used (LRU) Page Replacement Algorithm
#include <stdio.h>
#include <stdbool.h>

// Function which runs the algorithm and in the end, returns no. of page faults

int LRU_algorithm(int totalPages, int pages[], int totalFrames, int frames[])
{
    int i, j;
    int pageFaults = 0;

    for (i = 0; i < totalPages; i++)
    {
        int currentPage = pages[i];

        // Check if Page Already Exists
        bool found = false;
        int k;
        for (k = 0; k < totalFrames; k++)
        {
            if (frames[k] == currentPage)
            {
                found = true;
                break;
            }
        }
        // If Page Already Exists, Page Hit
        if (found == true)
        {
            int temp = frames[k];
            for(; k < totalFrames - 1; k++) // (This has to do something with current page, dk what's happening)
            {
                frames[k] = frames[k + 1];
            }
            frames[totalFrames - 1] = temp;
            for (j = 0; j < totalFrames; j++)
            {
                printf("%d \t", frames[j]);
            }
            printf("Page Hit !\n");
        }
        // If Not
        else
        {
            if(i < totalFrames)
            {
                frames[i] = currentPage;
            }
            else
            {
                for(k = 0; k < totalFrames - 1; k++)
                {
                    frames[k] = frames[k + 1];
                }
                frames[totalFrames - 1] = currentPage;
            }
            // Increment Page Faults
            pageFaults++;
            for (j = 0; j < totalFrames; j++)
            {
                printf("%d \t", frames[j]);
            }
            printf("Page Fault !\n");
        }
    }
    return pageFaults;
}

int main()
{
    int totalPages = 13;
    int pages[] = {7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2};

    int totalFrames = 4;
    int frames[totalFrames];

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

    printf("Total Number of Page Faults = %d\n", LRU_algorithm(totalPages, pages, totalFrames, frames));
}