磁盘调度算法（FCFS&&SSTF）

操作系统磁盘调度算法之FCFS和SSTF篇，我感觉自己写的好垃圾啊！！！

#include <iostream>#include <cstdlib>using namespace std;void FCFS(int a[],int n){    int sum = 0;    int i,j,now;    float avg;    cout << "请输入当前的磁道号:";    cin >> now;//确定当前磁头所在位置    cout << "磁盘调度顺序为:" << endl;    for(i = 0; i < n; i++)//按访问顺序输出磁道号    {        cout << a[i] <<" ";    }    cout << endl;    sum += abs(a[0] - now);    cout << "从当前位置到第1个磁道移动的磁道数为：" << sum << endl;    for(i = 0,j = 1; j < n; i++,j++)    {        sum += abs(a[j] - a[i]);//外围磁道与最里面磁道的距离        cout << "从第" << i+1 << "个磁道到第" << j+1 << "个磁道的移动距离为:" << abs(a[j] - a[i]) << endl;    }    cout << endl;    cout << "移动的总磁道数为:" << sum <<endl;    avg = sum * 1.0 / n;    cout << "平均寻道长度为:" << avg << endl;}void SSTF(int a[],int n){    int temp;    int now,L,r;    int j,i;    int k = 1;    int sum = 0;    float AVG;    //冒泡排序法对磁道号进行排序    for(i = 0; i < n; i++)        for(j = i + 1; j < n; j++)    {        if(a[i] > a[j])        {            temp = a[i];            a[i] = a[j];            a[j] = temp;        }    }    cout <<"按递增顺序排好的磁道：" << endl;    for(i = 0; i < n; i++)        cout << a[i] << " ";//输出排好的磁道顺序    cout << endl;    cout << "请输入当前的磁道号:";    cin >> now;//确定当前磁头所在位置    cout << "磁盘调度顺序为:" << endl;    if(now >= a[n-1])//当前磁头位置大于最外层欲访问磁道    {        for(i = n-1; i >= 0; i--)            cout << a[i] << " " << endl;//则磁盘调用从大到小        cout << "从当前位置到第1个磁道移动的磁道数为：" << now - a[n-1] << endl;        for(i = 0,j = 1; j < n; i++,j++)            cout << "从第" << i+1 << "个磁道到第" << j+1 << "个磁道的移动距离为:" << abs(a[j] - a[i]) << endl;        sum = now - a[0];//(now - a[n-1]) + (a[n-1) - a[n-2]) + .... + (a[1] -a[0])    }    else if(now < a[0])//当前磁头位置小于最外层欲访问磁道    {        for(i = 0; i < n; i++)            cout << a[i] << " " << endl;//则磁盘调用从小到大        cout << "从当前位置到第1个磁道移动的磁道数为：" << a[0] - now << endl;        for(i = 0,j = 1; j < n; i++,j++)            cout << "从第" << i+1 << "个磁道到第" << j+1 << "个磁道的移动距离为:" << abs(a[j] - a[i]) << endl;        sum = a[n-1] - now;//同上面    }    else    {        while(a[k] < now)            k++;//确定当前磁道在已排序的序列中的位置        L = k -1;//在磁头位置的前一个欲访问磁道        r = k;//磁头欲访问位置        while((L >= 0) && (r < n))        {            if((now - a[L]) <= (a[r] - now))//选择离磁头近的磁道            {                cout << a[L] << " ";                sum += now - a[L];                now = a[L];//将磁头位置移到第L个                L--;//L减一，准备好下一个            }            else            {                cout << a[r] << " ";                sum += a[r] - now;                now = a[r];//将磁头位置移到第r个                r++;//r增一，准备好下一个            }        }        if(L = -1)//磁头位置里侧的磁道已访问完        {            for(j = r; j < n; j++)                cout << a[j] << " ";            sum += a[n-1] -a[0];        }        if(r == n)        {            for(j = k - 1; j > -1; j--)                cout << a[j] << " ";            sum += a[n-1] - a[0];        }    }        cout << endl;        cout << "移动的总磁道数:" << sum <<endl;        AVG = sum * 1.0 / n;        cout << "平均寻道长度为:" << AVG << endl;}int main(){    int n;//此道的个数    int s;//功能号    int i;    cout << "请输入磁道个数:" << endl;    cin >> n;    int *a = new int[n];    for(i = 0;i < n; i++)    {        cout << "请输入第" << i+1 << "个磁道号:";        cin >> a[i];    }    cout << endl;    while(1)    {        cout << endl;        cout << "1:先来先服务算法:" << endl;        cout << "2:最短寻道时间算法:" << endl;        cout << "0:退出" << endl;        cout << endl;        cout << "请选择功能号:";        cin >> s;        if(s > 2)        {            cout << "输入错误！" << endl;        }        else        {            switch(s)            {                case 0:exit(0);break;                case 1:FCFS(a,n);break;                case 2:SSTF(a,n);break;            }        }    }    return 0;}