作業系統磁碟排程演算法之FCFS和SSTF篇，我感覺自己寫的好垃圾啊！！！

#include <iostream>
#include <cstdlib>
using namespace std;
void FCFS(int a[],int n)
{
    int sum = 0;
    int i,j,now;
    float avg;
    cout << "請輸入當前的磁軌號:";
    cin >> now;//確定當前磁頭所在位置
    cout << "磁碟排程順序為:" << endl;
    for
 
(i = 0; i < n; i++)//按訪問順序輸出磁軌號
    {
        cout << a[i] <<" ";
    }
    cout << endl;
    sum += abs(a[0] - now);
    cout << "從當前位置到第1個磁軌移動的磁軌數為：" << sum << endl;
    for(i = 0,j = 1; j < n; i++,j++)
    {
        sum += abs(a[j] - a[i]);//外圍磁軌與最裡面磁軌的距離
        cout
 
 << "從第" << i+1 << "個磁軌到第" << j+1 << "個磁軌的移動距離為:" << abs(a[j] - a[i]) << endl;
    }
    cout << endl;
    cout << "移動的總磁軌數為:" << sum <<endl;
    avg = sum * 1.0 / n;
    cout << "平均尋道長度為:" << 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;
    //氣泡排序法對磁軌號進行排序
    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 <<"按遞增順序排好的磁軌：" << endl;
    for(i = 0; i < n; i++)
        cout << a[i] << " ";//輸出排好的磁軌順序
    cout << endl;
    cout << "請輸入當前的磁軌號:";
    cin >> now;//確定當前磁頭所在位置
    cout << "磁碟排程順序為:" << endl;
    if(now >= a[n-1])//當前磁頭位置大於最外層欲訪問磁軌
    {
        for(i = n-1; i >= 0; i--)
            cout << a[i] << " " << endl;//則磁碟呼叫從大到小
        cout << "從當前位置到第1個磁軌移動的磁軌數為：" << now - a[n-1] << endl;
        for(i = 0,j = 1; j < n; i++,j++)
            cout << "從第" << i+1 << "個磁軌到第" << j+1 << "個磁軌的移動距離為:" << 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])//當前磁頭位置小於最外層欲訪問磁軌
    {
        for(i = 0; i < n; i++)
            cout << a[i] << " " << endl;//則磁碟呼叫從小到大
        cout << "從當前位置到第1個磁軌移動的磁軌數為：" << a[0] - now << endl;
        for(i = 0,j = 1; j < n; i++,j++)
            cout << "從第" << i+1 << "個磁軌到第" << j+1 << "個磁軌的移動距離為:" << abs(a[j] - a[i]) << endl;
        sum = a[n-1] - now;//同上面
    }
    else
    {
        while(a[k] < now)
            k++;//確定當前磁軌在已排序的序列中的位置
        L = k -1;//在磁頭位置的前一個欲訪問磁軌
        r = k;//磁頭欲訪問位置
        while((L >= 0) && (r < n))
        {
            if((now - a[L]) <= (a[r] - now))//選擇離磁頭近的磁軌
            {
                cout << a[L] << " ";
                sum += now - a[L];
                now = a[L];//將磁頭位置移到第L個
                L--;//L減一，準備好下一個
            }
            else
            {
                cout << a[r] << " ";
                sum += a[r] - now;
                now = a[r];//將磁頭位置移到第r個
                r++;//r增一，準備好下一個
            }
        }
        if(L = -1)//磁頭位置裡側的磁軌已訪問完
        {
            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 << "移動的總磁軌數:" << sum <<endl;
        AVG = sum * 1.0 / n;
        cout << "平均尋道長度為:" << AVG << endl;
}

int main()
{
    int n;//此道的個數
    int s;//功能號
    int i;
    cout << "請輸入磁軌個數:" << endl;
    cin >> n;
    int *a = new int[n];
    for(i = 0;i < n; i++)
    {
        cout << "請輸入第" << i+1 << "個磁軌號:";
        cin >> a[i];
    }
    cout << endl;
    while(1)
    {
        cout << endl;
        cout << "1:先來先服務演算法:" << endl;
        cout << "2:最短尋道時間演算法:" << endl;
        cout << "0:退出" << endl;
        cout << endl;
        cout << "請選擇功能號:";
        cin >> s;
        if(s > 2)
        {
            cout << "輸入錯誤！" << endl;
        }
        else
        {
            switch(s)
            {
                case 0:exit(0);break;
                case 1:FCFS(a,n);break;
                case 2:SSTF(a,n);break;
            }
        }
    }
    return 0;
}