12c.c

// Disk Scheduling Algorithms
// Circular Scan
// by Simply


#include <stdio.h>

void cscan(int req[], int n, int head, int max)
{
    int seek = 0, c = 0, temp, i, j, seq[20];

    for (i = 0; i < n - 1; i++)
    {
        for (j = 0; j < n - i - 1; j++)
        {
            if (req[j] > req[j + 1])
            {
                temp = req[j];
                req[j] = req[j + 1];
                req[j + 1] = temp;
            }
        }
    }

    j = 0;
    while (req[j] <= head)
        j++;

    for (i = j; i < n; i++) {
        seek += req[i] - head;
        head = req[i];
        seq[c] = req[i];
        c++;
    }

    seek += (max - 1) - req[n - 1];
    head = max - 1;

    for (i = 0; i < j; i++) {
        seek += head - req[i];
        head = req[i];
        seq[c] = req[i];
        c++;
    }

    printf("TIME TO SEEK = %d\n", seek);
    printf("SEEK SEQUENCE: ");
    for (i = 0; i < c; i++)
        printf("%d->", seq[i]);
}

void main()
{
    int head, req[20], n, i, max, flag = 0;
    
    printf("NUMBER OF CYLINDERS: ");
    scanf("%d", &max);
    
    printf("NUMBER OF REQUESTS: ");
    scanf("%d", &n);
    
    printf("ENTER REQUESTS: ");
    for (i = 0; i < n; i++)
        scanf("%d", &req[i]);

    printf("POSITION OF READER / WRITER: ");
    scanf("%d", &head);

    if (req[0] > max - 1)
        flag = 1;
    
    if (flag == 1)
        printf("CANNOT BE COMPLETED");
    else
        cscan(req, n, head, max);
}