磁盘调度算法c语言实现

以下是几种常见磁盘调度算法的C语言实现：

1. 先来先服务（FCFS）算法

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
    int queue[1000], head, n, i, j, seek_time = 0;

    printf("Enter the number of requests: ");
    scanf("%d", &n);
    printf("Enter the request queue: ");
    for(i=0; i<n; i++)
        scanf("%d", &queue[i]);
    printf("Enter the initial head position: ");
    scanf("%d", &head);

    for(i=0; i<n; i++)
    {
        seek_time += abs(head - queue[i]);
        head = queue[i];
    }

    printf("Total seek time: %d\n", seek_time);

    return 0;
}

2. 最短寻道时间优先（SSTF）算法

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int find_closest(int queue[], int n, int head, int visited[])
{
    int min_dist = 100000, index = -1, i;
    for(i=0; i<n; i++)
    {
        if(!visited[i])
        {
            int dist = abs(head - queue[i]);
            if(dist < min_dist)
            {
                index = i;
                min_dist = dist;
            }
        }
    }
    return index;
}

int main()
{
    int queue[1000], head, n, i, j, seek_time = 0, visited[1000] = {0};

    printf("Enter the number of requests: ");
    scanf("%d", &n);
    printf("Enter the request queue: ");
    for(i=0; i<n; i++)
        scanf("%d", &queue[i]);
    printf("Enter the initial head position: ");
    scanf("%d", &head);

    for(i=0; i<n; i++)
    {
        int index = find_closest(queue, n, head, visited);
        visited[index] = 1;
        seek_time += abs(head - queue[index]);
        head = queue[index];
    }

    printf("Total seek time: %d\n", seek_time);

    return 0;
}

3. 扫描（SCAN）算法

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
    int queue[1000], head, n, i, j, seek_time = 0;

    printf("Enter the number of requests: ");
    scanf("%d", &n);
    printf("Enter the request queue: ");
    for(i=0; i<n; i++)
        scanf("%d", &queue[i]);
    printf("Enter the initial head position: ");
    scanf("%d", &head);

    int direction = 1; // 1 for up, -1 for down
    for(i=0; i<n; i++)
    {
        if(direction == 1) // scanning up
        {
            int closest_index = -1, min_dist = 100000;
            for(j=0; j<n; j++)
            {
                if(queue[j] >= head && abs(queue[j] - head) < min_dist)
                {
                    closest_index = j;
                    min_dist = abs(queue[j] - head);
                }
            }
            if(closest_index == -1) // no requests above head
            {
                direction = -1;
                seek_time += abs(queue[n-1] - head); // go to the end
                head = queue[n-1];
            }
            else
            {
                seek_time += abs(queue[closest_index] - head);
                head = queue[closest_index];
            }
        }
        else // scanning down
        {
            int closest_index = -1, min_dist = 100000;
            for(j=0; j<n; j++)
            {
                if(queue[j] <= head && abs(queue[j] - head) < min_dist)
                {
                    closest_index = j;
                    min_dist = abs(queue[j] - head);
                }
            }
            if(closest_index == -1) // no requests below head
            {
                direction = 1;
                seek_time += abs(queue[0] - head); // go to the beginning
                head = queue[0];
            }
            else
            {
                seek_time += abs(queue[closest_index] - head);
                head = queue[closest_index];
            }
        }
    }

    printf("Total seek time: %d\n", seek_time);

    return 0;
}

4. 循环扫描（C-SCAN）算法

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
    int queue[1000], head, n, i, j, seek_time = 0;

    printf("Enter the number of requests: ");
    scanf("%d", &n);
    printf("Enter the request queue: ");
    for(i=0; i<n; i++)
        scanf("%d", &queue[i]);
    printf("Enter the initial head position: ");
    scanf("%d", &head);

    int direction = 1; // 1 for up, -1 for down
    for(i=0; i<n; i++)
    {
        if(direction == 1) // scanning up
        {
            int closest_index = -1, min_dist = 100000;
            for(j=0; j<n; j++)
            {
                if(queue[j] >= head && abs(queue[j] - head) < min_dist)
                {
                    closest_index = j;
                    min_dist = abs(queue[j] - head);
                }
            }
            if(closest_index == -1) // no requests above head
            {
                direction = -1;
                seek_time += abs(queue[n-1] - head) + abs(queue[n-1] - queue[0]); // go to the end and then to the beginning
                head = queue[0];
            }
            else
            {
                seek_time += abs(queue[closest_index] - head);
                head = queue[closest_index];
            }
        }
        else // scanning down
        {
            int closest_index = -1, min_dist = 100000;
            for(j=0; j<n; j++)
            {
                if(queue[j] <= head && abs(queue[j] - head) < min_dist)
                {
                    closest_index = j;
                    min_dist = abs(queue[j] - head);
                }
            }
            if(closest_index == -1) // no requests below head
            {
                direction = 1;
                seek_time += abs(queue[n-1] - head) + abs(queue[n-1] - queue[0]); // go to the end and then to the beginning
                head = queue[0];
            }
            else
            {
                seek_time += abs(queue[closest_index] - head);
                head = queue[closest_index];
            }
        }
    }

    printf("Total seek time: %d\n", seek_time);

    return 0;
}