LRU

#include <stdio.h>

int findLRU(int time[], int frames) {
    int i, minIndex = 0;
    for (i = 1; i < frames; i++) {
        if (time[i] < time[minIndex])
            minIndex = i;
    }
    return minIndex;
}

int main() {
    int frames, pages, i, j, pageFaults = 0, time[10], counter = 0;

    printf("Enter the number of frames: ");
    scanf("%d", &frames);

    printf("Enter the number of pages: ");
    scanf("%d", &pages);

    int pageArray[pages], frameArray[frames];

    printf("Enter the page reference sequence: ");
    for (i = 0; i < pages; i++)
        scanf("%d", &pageArray[i]);

    for (i = 0; i < frames; i++)
        frameArray[i] = -1;  // Initialize frames as empty

    printf("\nPage Replacement Process:\n");

    for (i = 0; i < pages; i++) {
        int found = 0;

        // Check if the page is already in a frame
        for (j = 0; j < frames; j++) {
            if (frameArray[j] == pageArray[i]) {
                found = 1;
                time[j] = counter++;  // Update usage time
                break;
            }
        }

        // If page is not found, replace the LRU page
        if (!found) {
            int replaceIndex = (i < frames) ? i : findLRU(time, frames);
            frameArray[replaceIndex] = pageArray[i];
            time[replaceIndex] = counter++;  // Store time of use
            pageFaults++;

            // Display frames after replacement
            printf("Page %d -> Frames: ", pageArray[i]);
            for (j = 0; j < frames; j++)
                printf("%d ", frameArray[j]);
            printf("\n");
        }
    }

    printf("\nTotal Page Faults: %d\n", pageFaults);
    return 0;
}