利用先来先服务FCFS,最短寻道时间优先SSTF,SCAN和循环SCAN算法模拟磁道访问过程, 模拟四种算法的磁道访问过程,给出每个磁道访问的磁头移动距离, 输入:磁道个数n和磁道访问序列,开始磁道号m和磁头移动方向(对SCAN和循环SCAN算法有效),算法选择1-FCFS,2-SSTF,3-SCAN,4-循环SCAN,输出:每种算法的平均寻道长度,用Java实现
时间: 2024-01-30 12:02:26 浏览: 22
好的,我会尽力回答你的问题。这是一个关于磁盘调度算法的问题,需要实现四种算法并计算它们的平均寻道长度。下面是一个 Java 实现的示例代码:
```java
import java.util.*;
public class DiskScheduling {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
// 输入磁道个数n和磁道访问序列
System.out.print("请输入磁道个数n:");
int n = scan.nextInt();
System.out.print("请输入磁道访问序列,以空格分隔:");
int[] requests = new int[n];
for (int i = 0; i < n; i++) {
requests[i] = scan.nextInt();
}
// 输入开始磁道号m和磁头移动方向
System.out.print("请输入开始磁道号m:");
int m = scan.nextInt();
System.out.print("请输入磁头移动方向(1表示向内,-1表示向外):");
int direction = scan.nextInt();
// 选择算法
System.out.print("请选择磁盘调度算法(1-FCFS,2-SSTF,3-SCAN,4-循环SCAN):");
int algorithm = scan.nextInt();
// 调用相应的算法计算平均寻道长度
double avgSeekTime = 0;
switch (algorithm) {
case 1:
avgSeekTime = fcfs(requests, m);
break;
case 2:
avgSeekTime = sstf(requests, m);
break;
case 3:
avgSeekTime = scan(requests, m, direction);
break;
case 4:
avgSeekTime = cscan(requests, m);
break;
default:
System.out.println("输入错误,请重新输入!");
return;
}
// 输出平均寻道长度
System.out.println("平均寻道长度为:" + avgSeekTime);
}
// 先来先服务算法
public static double fcfs(int[] requests, int head) {
int n = requests.length;
int distance = 0;
for (int i = 0; i < n; i++) {
distance += Math.abs(requests[i] - head);
head = requests[i];
}
return (double) distance / n;
}
// 最短寻道时间优先算法
public static double sstf(int[] requests, int head) {
int n = requests.length;
int[] visited = new int[n];
Arrays.fill(visited, 0);
int distance = 0;
for (int i = 0; i < n; i++) {
int minDistance = Integer.MAX_VALUE;
int index = 0;
for (int j = 0; j < n; j++) {
if (visited[j] == 0 && Math.abs(requests[j] - head) < minDistance) {
minDistance = Math.abs(requests[j] - head);
index = j;
}
}
visited[index] = 1;
distance += minDistance;
head = requests[index];
}
return (double) distance / n;
}
// SCAN算法
public static double scan(int[] requests, int head, int direction) {
int n = requests.length;
Arrays.sort(requests);
int index = 0;
for (int i = 0; i < n; i++) {
if (requests[i] > head) {
index = i;
break;
}
}
int distance = 0;
if (direction == 1) {
if (index != 0) {
for (int i = index - 1; i >= 0; i--) {
distance += head - requests[i];
head = requests[i];
}
}
distance += head;
head = 0;
for (int i = index; i < n; i++) {
distance += requests[i] - head;
head = requests[i];
}
} else {
if (index != n) {
for (int i = index; i < n; i++) {
distance += requests[i] - head;
head = requests[i];
}
}
distance += 2 * (n - index) * head;
head = n - 1;
for (int i = index - 1; i >= 0; i--) {
distance += head - requests[i];
head = requests[i];
}
}
return (double) distance / n;
}
// 循环SCAN算法
public static double cscan(int[] requests, int head) {
int n = requests.length;
Arrays.sort(requests);
int index = 0;
for (int i = 0; i < n; i++) {
if (requests[i] > head) {
index = i;
break;
}
}
int distance = 0;
if (index != 0) {
for (int i = index - 1; i >= 0; i--) {
distance += head - requests[i];
head = requests[i];
}
}
distance += head;
head = n - 1;
for (int i = n - 1; i >= index; i--) {
distance += head - requests[i];
head = requests[i];
}
distance += head;
return (double) distance / n;
}
}
```
以上代码实现了四种算法,分别是先来先服务算法(FCFS)、最短寻道时间优先算法(SSTF)、SCAN算法和循环SCAN算法。在输入磁道个数、磁道访问序列、开始磁道号和磁头移动方向后,可以选择相应的算法计算平均寻道长度。
其中,FCFS算法和SSTF算法比较简单,直接按照请求的顺序处理即可,计算距离时需要加上磁头移动的距离。SCAN算法和循环SCAN算法需要先将请求按照磁道号排序,然后根据磁头移动方向和当前磁头所在位置确定扫描的顺序。计算距离时需要考虑磁头的移动方向,以及到达边界时的特殊情况。最后,将计算出的总距离除以磁道个数,即可得到平均寻道长度。
希望这个代码能够解决你的问题,如果还有其他疑问,请随时提出。