操作系统——调度算法FCFS、SSTF、SCAN、C-SCAN（C++实现）

首先，指出一个已经知道的BUG，就是排序用了地址传递使得，先运行SSTF或SCAN或C-SCAN后会影响FCFS

所以要得到正确的FCFS的运行结果，必须第一次运行就用FCFS。注意需要在cpp源文件目录里新建一个cidao.txt文件，然后复制粘贴下面这一段：

98 138 37 122 14 124 65 67

这里给出代码：

#include"stdio.h"
#include"stdlib.h"
#include<iostream>
#define maxsize 100
using namespace std;


void FCFS(int array[], int m)
{
	int sum = 0, now;
	cout << "请输入当前磁道号：";
	cin >> now;
	for (int i = 0; i < m; i++)
	{
		cout << array[i] << " ";
	}
	sum += abs(now - array[0]);
	for (int i = 0, j = 1; j < m; i++, j++)
	{
		sum += abs(array[j] - array[i]);
	}
	cout << "移动的总道数：" << sum << endl;
}

void ShortPath(int array[], int m)
{
	int temp;
	int k = 1;
	int now, l, r;
	int i, j, sum = 0;
	for(i=0;i<m;i++)
		for (j = i + 1; j < m; j++)
		{
			if (array[i] > array[j])
			{
				temp = array[i];
				array[i] = array[j];
				array[j] = temp;
			}
		}
	for (i = 0; i < m; i++)
	{
		cout << array[i] << " ";
	}
	cout << "请输入当前的磁道号：";
	cin >> now;
	if (array[m - 1] <= now)
	{
		for (i = m; i >= 0; i--)
			cout << array[i] << ' ';
		sum = now - array[0];
	}
	else
		if (array[0] >= now)
		{
			for (i = 0; i < m; i++)
				cout << array[i] << ' ';
			sum = array[m - 1] - now;
		}
		else
		{
			while (array[k] < now)
			{
				k++;
			}
			l = k - 1;
			r = k;
			while ((l >= 0) && (r < m))
			{
				if ((now - array[l]) <= (array[r] - now))
				{
					cout << array[l] << " ";
					sum += now - array[l];
					now = array[l];
					l = l - 1;
				}
				else
				{
					cout << array[r] << ' ';
					sum += array[r] - now;
					now = array[r];
					r = r + 1;
				}
			}
			if (l = -1)
			{
				for (j = r; j < m; j++)
				{
					cout << array[j] << ' ';
				}
				sum += array[m - 1] - array[0];
			}
			else
			{
				for (j = i; j >= 0; j--)
				{
					cout << array[j] << ' ';
				}
				sum += array[m - 1] - array[0];
			}
		}
	cout << "移动的总道数：" << sum << endl;
}

void Elevator(int array[], int m)
{
	int temp;
	int k = 1;
	int now, l, r, d;
	int i, j, sum = 0;
	for(i=0;i<m;i++)
		for (j = i + 1; j < m; j++)
		{
			if (array[i] > array[j])
			{
				temp = array[i];
				array[i] = array[j];
				array[j] = temp;
			}
		}
	for (i = 0; i < m; i++)
	{
		cout << array[i] << ' ';
	}
	cout << "请输入当前的磁道号：";
	cin >> now;
	if (array[m - 1] <= now)
	{
		for (i = m - 1; i < m; i++)
			cout << array[i] << ' ';
		sum = array[m - 1] - now;
	}
	else
	{
		while (array[k] < now)
		{
			k++;
		}
		l = k - 1;
		r = k;
		cout << "请输入当前移动臂的移动的方向（1表示向内，0表示向外）：";
		cin >> d;
		if (d == 0)
		{
			for (j = l; j >= 0; j--)
			{
				cout << array[j] << ' ';
			}
			for (j = r; j < m; j++)
			{
				cout << array[j] << ' ';
			}
			sum = now - 2 * array[0] + array[m - 1];
		}
		else
		{
			for (j = r; j < m; j++)
			{
				cout << array[j] << ' ';
			}
			for (j = l; j >= 0; j--)
			{
				cout << array[j] << ' ';
			}
			sum = -now - array[0] + 2 * array[m - 1];
		}
	}
	cout << "移动的总道数：" << sum << endl;
}

void CSCAN(int array[], int m)
{
	int temp;
	int k = 1;
	int now, l, r, d;
	int i, j, sum = 0;
	for (i = 0; i < m; i++)
		for (j = i + 1; j < m; j++)
		{
			if (array[i] > array[j])
			{
				temp = array[i];
				array[i] = array[j];
				array[j] = temp;
			}
		}
	for (i = 0; i < m; i++)
	{
		cout << array[i] << ' ';
	}
	cout << "请输入当前的磁道号：";
	cin >> now;
	if (array[m - 1] <= now)
	{
		for (i = m - 1; i < m; i++)
			cout << array[i] << ' ';
		sum = array[m - 1] - now;
	}
	else
	{
		while (array[k] < now)
		{
			k++;
		}
		l = k - 1;
		r = k;
		cout << "请输入当前移动臂的移动的方向（1表示向内，0表示向外）：";
		cin >> d;
		if (d == 0)
		{
			for (j = l; j >= 0; j--)
			{
				cout << array[j] << ' ';
			}
			for (j = m - 1; j >=k; j--)
			{
				cout << array[j] << ' ';
			}
			sum = now - 2 * array[0] + array[m - 1];
		}
		else
		{
			for (j = r; j < m; j++)
			{
				cout << array[j] << ' ';
			}
			for (j = 0; j < k; j++)
			{
				cout << array[j] << ' ';
			}
			sum = -now - array[0] + 2 * array[m - 1];
		}
	}
	cout << "移动的总道数：" << sum << endl;
}


int main(void)
{
	int c;
	FILE *fp;
	int cidao[maxsize];
	int i = 0, count;
	fp = fopen("cidao.txt", "r+");
	if (fp == NULL)
	{
		cout << "文件打不开！" << endl;
		exit(0);
	}
	while (!feof(fp))
	{
		fscanf(fp, "%d", &cidao[i]);
		i++;
	}
	count = i;

	for (i = 0; i < count; i++)
	{
		printf("%5d", cidao[i]);
	}
	cout << endl;
	while (true)
	{
		cout << endl << "系统菜单如下：" << endl;
		printf("1.先来先服务           2.最短寻道时间优先            3.电梯调度           4.CSCAN");
		cout << endl;
		cout << "请选择：";
		cin >> c;
		if (c > 4)break;
		switch (c)
		{
		case 1:
			FCFS(cidao, count);
			break;
		case 2:
			ShortPath(cidao, count);
			break;
		case 3:
			Elevator(cidao, count);
			break;
		case 4:
			CSCAN(cidao, count);
			break;
		}
	}
	system("pause");
	return 0;
}

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