银行家算法

#include<stdio.h>
#include<iostream>
using namespace std;
#define resourceNum 3
#define processNum  5

//系统可用（剩余）资源
int available[resourceNum] = { 3, 3, 2 };
//进程的最大需求
int maxRequest[processNum][resourceNum] = { { 7, 5, 3 }, { 3, 2, 2 }, { 9, 0, 2 }, { 2, 2, 2 }, { 4, 3, 3 } };
//进程已经占有（分配）资源
int allocation[processNum][resourceNum] = { { 0, 1, 0 }, { 2, 0, 0 }, { 3, 0, 2 }, { 2, 1, 1 }, { 0, 0, 2 } };
//进程还需要资源
int need[processNum][resourceNum] = { { 7, 4, 3 }, { 1, 2, 2 }, { 6, 0, 0 }, { 0, 1, 1 }, { 4, 3, 1 } };
//是否安全
bool Finish[processNum];
//安全序列号
int safeSeries[processNum] = { 0, 0, 0, 0, 0 };
//进程请求资源量
int request[resourceNum];
//资源数量计数
int num;

//打印输出系统信息
void showInfo()
{
	printf("\n------------------------------------------------------------------------------------\n");
	printf("当前系统各类资源剩余：");
	for (int j = 0; j < resourceNum; j++)
	{
		printf("%d ", available[j]);
	}
	printf("\n\n当前系统资源情况：\n");
	printf(" PID\t Max\t\tAllocation\t Need\n");
	for (int i = 0; i < processNum; i++)
	{
		printf(" P%d\t", i);
		for (int j = 0; j < resourceNum; j++)
		{
			printf("%2d", maxRequest[i][j]);
		}
		printf("\t\t");
		for (int j = 0; j < resourceNum; j++)
		{
			printf("%2d", allocation[i][j]);
		}
		printf("\t\t");
		for (int j = 0; j < resourceNum; j++)
		{
			printf("%2d", need[i][j]);
		}
		printf("\n");
	}
}

//打印安全检查信息
void SafeInfo(int *work, int i)
{
	int j;
	printf(" P%d\t", i);
	for (j = 0; j < resourceNum; j++)
	{
		printf("%2d", work[j]);
	}
	printf("\t\t");
	for (j = 0; j < resourceNum; j++)
	{
		printf("%2d", allocation[i][j]);
	}
	printf("\t\t");
	for (j = 0; j < resourceNum; j++)
	{
		printf("%2d", need[i][j]);
	}
	printf("\t\t");
	for (j = 0; j < resourceNum; j++)
	{
		printf("%2d", allocation[i][j] + work[j]);
	}
	printf("\n");
}

//判断一个进程的资源是否全为零
bool isAllZero(int kang)
{
	num = 0;
	for (int i = 0; i < resourceNum; i++)
	{
		if (need[kang][i] == 0)
		{
			num++;
		}
	}
	if (num == resourceNum)
	{
		return true;
	}
	else
	{
		return false;
	}
}

//安全检查
bool isSafe()
{
	//int resourceNumFinish = 0;
	int safeIndex = 0;
	int allFinish = 0;
	int work[resourceNum] = { 0 };
	int r = 0;
	int temp = 0;
	int pNum = 0;
	//预分配为了保护available[]
	for (int i = 0; i < resourceNum; i++)
	{
		work[i] = available[i];
	}
	//把未完成进程置为false
	for (int i = 0; i < processNum; i++)
	{
		bool result = isAllZero(i);
		if (result == true)
		{
			Finish[i] = true;
			allFinish++;
		}
		else
		{
			Finish[i] = false;
		}

	}
	//预分配开始
	while (allFinish != processNum)
	{
		num = 0;
		for (int i = 0; i < resourceNum; i++)
		{
			if (need[r][i] <= work[i] && Finish[r] == false)
			{
				num++;
			}
		}
		if (num == resourceNum)
		{
			for (int i = 0; i < resourceNum; i++)
			{
				work[i] = work[i] + allocation[r][i];
			}
			allFinish++;
			SafeInfo(work, r);
			safeSeries[safeIndex] = r;
			safeIndex++;
			Finish[r] = true;
		}
		r++;//该式必须在此处	
		if (r >= processNum)
		{
			r = r % processNum;
			if (temp == allFinish)
			{
				break;
			}
			temp = allFinish;
		}
		pNum = allFinish;
	}
	//判断系统是否安全
	for (int i = 0; i < processNum; i++)
	{
		if (Finish[i] == false)
		{
			printf("\n当前系统不安全！\n\n");
			return false;
		}
	}
	//打印安全序列
	printf("\n当前系统安全！\n\n安全序列为：");
	for (int i = 0; i < processNum; i++)
	{
		bool result = isAllZero(i);
		if (result == true)
		{
			pNum--;
		}
	}
	for (int i = 0; i < pNum; i++)
	{
		printf("%d ", safeSeries[i]);
	}
	return true;
}

//主函数
void main()
{
	int curProcess = 0;
	int a = -1;
	showInfo();
	printf("\n系统安全情况分析\n");
	printf(" PID\t Work\t\tAllocation\t Need\t\tWork+Allocation\n");
	bool isStart = isSafe();
	//用户输入或者预设系统资源分配合理才能继续进行进程分配工作
	while (isStart)
	{
		//限制用户输入，以防用户输入大于进程数量的数字，以及输入其他字符（乱输是不允许的）
		do
		{
			if (curProcess >= processNum || a == 0)
			{
				printf("\n请不要输入超出进程数量的值或者其他字符：\n");
				while (getchar() != '\n'){};//清空缓冲区	
				a = -1;
			}
			printf("\n------------------------------------------------------------------------------------\n");
			printf("\n输入要分配的进程：");
			a = scanf("%d", &curProcess);
			printf("\n");

		} while (curProcess >= processNum || a == 0);

		//限制用户输入，此处只接受数字，以防用户输入其他字符（乱输是不允许的）
		for (int i = 0; i < resourceNum; i++)
		{
			do
			{
				if (a == 0)
				{
					printf("\n请不要输入除数字以外的其他字符，请重新输入：\n");
					while (getchar() != '\n'){};//清空缓冲区	
					a = -1;
				}
				printf("请输入要分配给进程 P%d 的第 %d 类资源：", curProcess, i + 1);
				a = scanf("%d", &request[i]);
			} while (a == 0);
		}

		//判断用户输入的分配是否合理，如果合理，开始进行预分配
		num = 0;
		for (int i = 0; i < resourceNum; i++)
		{
			if (request[i] <= need[curProcess][i] && request[i] <= available[i])
			{
				num++;
			}
			else
			{
				printf("\n发生错误！可能原因如下：\n(1)您请求分配的资源可能大于该进程的某些资源的最大需要！\n(2)系统所剩的资源已经不足了！\n");
				break;
			}
		}
		if (num == resourceNum)
		{
			num = 0;
			for (int j = 0; j < resourceNum; j++)
			{
				//分配资源
				available[j] = available[j] - request[j];
				allocation[curProcess][j] = allocation[curProcess][j] + request[j];
				need[curProcess][j] = need[curProcess][j] - request[j];
				//记录分配以后，是否该进程需要值为0了
				if (need[curProcess][j] == 0)
				{
					num++;
				}
			}
			//如果分配以后出现该进程对所有资源的需求为0了，即刻释放该进程占用资源（视为完成）
			if (num == resourceNum)
			{
				//释放已完成资源
				for (int i = 0; i < resourceNum; i++)
				{
					available[i] = available[i] + allocation[curProcess][i];
				}
				printf("\n\n本次分配进程 P%d 完成,该进程占用资源全部释放完毕！\n", curProcess);
			}
			else
			{
				//资源分配可以不用一次性满足进程需求
				printf("\n\n本次分配进程 P%d 未完成！\n", curProcess);
			}

			showInfo();
			printf("\n系统安全情况分析\n");
			printf(" PID\t Work\t\tAllocation\t Need\t\tWork+Allocation\n");

			//预分配完成以后，判断该系统是否安全，若安全，则可继续进行分配，若不安全，将已经分配的资源换回来
			if (!isSafe())
			{
				for (int j = 0; j < resourceNum; j++)
				{
					available[j] = available[j] + request[j];
					allocation[curProcess][j] = allocation[curProcess][j] - request[j];
					need[curProcess][j] = need[curProcess][j] + request[j];
				}
				printf("资源不足，等待中...\n\n分配失败！\n");
			}
		}
	}
}