利用银行家算法避免死锁（C++实现）

算法思想：

代码：

#include
#include
using namespace std;
#define  numberOfProcess 5
#define  numberOfReSource 3
int *available=new int[numberOfReSource];
int *work=new int[numberOfReSource];
string *securitySequence=new string[numberOfProcess];
typedef struct pcb {
	string pName;//进程名
	string *nameOfReSource = new string[numberOfReSource];//依次存放各类资源的名称
	int *max = new int[numberOfReSource];//max[j]=K表示进程需要Rj类资源的最大数目为K
	int *allocation = new int[numberOfReSource];//allocation[j]=K表示进程已分得Rj类资源的数目为K
	int *need = new int[numberOfReSource];//need[j]=K表示进程还需要Rj类资源K个方能完成任务
	bool finish;
	struct pcb *next;//链接指针指向下一个进程
}PCB;

void printProcess(PCB* p) {//输出进程的相关信息
	PCB *q = p->next;//q指向第一个进程
	cout << endl << "所有进程的相关信息" << endl;
	cout << "         Need        Allocation    Finish" << endl;
	cout << "进程  A   B   C      A   B   C           " << endl;
	while (q) {//遍历进程
		cout << q->pName << "    ";
		cout << q->need[0] << "   " << q->need[1] << "   " << q->need[2] << "      ";
		cout << q->allocation[0] << "   " << q->allocation[1] << "   " << q->allocation[2] << "     ";
		cout << (q->finish ? "true" : "false") << endl;
		q = q->next;//q指向下一个进程
	}
	cout << endl;
}

void initProcess(PCB *p) {//初始化进程
	cout << "初始化进程" << endl;
	cout << "请依次输入资源的名称:";
	string *nameOfReSource = new string[numberOfReSource];//该变量里依次存放资源的名称
	for (int i = 0; i> nameOfReSource[i];
	cout << "请依次输入当前可利用资源量:";
	for (int i = 0; i> available[i];
	PCB *q = p;
	PCB *r = new PCB;//当前工作指针
	for (int i = 0; i> r->pName;
		cout << "请依次输入该进程的各类资源的最大需求量(例如:2 3 4 ...):";
		for (int j = 0; j> r->max[j];
		cout << "请依次输入该进程的各类资源的已经分配量(例如:2 3 4 ...):";
		for (int j = 0; j> r->allocation[j];
			r->need[j] = r->max[j] - r->allocation[j];
			r->finish = false;
		}
		q->next = r;
		q = r;
		r->next = new PCB;
		r = r->next;//指针后移
	}
	r->next = NULL;
	q->next = NULL;
	q = NULL;
	delete q;//释放结点
	delete r;
	printProcess(p);//输出此时进程的相关信息
	cout << endl;
}

bool securityAlgorithm(PCB *p) {//安全性检查算法
	PCB *m = p->next;//m指向第一个结点
	PCB *s = p->next;//s指向第一个结点
	int count = 0;
	bool flag = true;
	for (int i = 0; ifinish = false;
		s = s->next;
	}
	while (true) {//安全性检测
		flag = true;
		for (int j = 0; jneed[j]>work[j] && !m->finish) {
				flag = false;
				break;
			}
		if (flag && !m->finish) {//找到符合条件的进程
			securitySequence[count++] = m->pName;//将该进程的名称加到安全序列中
			for (int j = 0; jallocation[j];
			m->finish = true;//修改finish
			cout << endl << "当前选中的进程:" << m->pName << endl;
			cout << "该进程预分配后work变量的值:";//输出此刻work变量的值
			for (int j = 0; jnext;//m指向下一个进程
		if (m == NULL)//m指向第一个进程
			m = p->next;
		s = p->next;
		flag = false;
		for (int i = 0; ifinish) {
				s = s->next;
				continue;
			}
			flag = true;
			for (int j = 0; jneed[j]>work[j]) {
					flag = false;
					break;
				}
			if (flag)//当前进程符合条件
				break;
			s = s->next;
		}
		if (!flag)//退出整个循环
			break;
	}
	flag = true;
	s = p->next;
	for (int i = 0; ifinish) {
			flag = false;
			break;
		}
		s = s->next;
	}
	if (flag) {//全为true
		cout << endl << "当前系统是安全的" << endl;
		cout << "安全序列:";
		for (int i = 0; i> nameOfRequestResource;
		cout << "请依次输入请求向量:";
		for (int i = 0; i> requestResource[i];
		}
		q = p->next;
		while (q) {//找到当前进程
			if (q->pName == nameOfRequestResource)
				break;
			q = q->next;
		}
		cout << endl << "银行家算法开始进行检查" << endl << endl;
		flag = true;
		for (int i = 0; iq->need[i] || requestResource[i]>available[i]) {
				flag = false;
				break;
			}
		}
		if (flag) {//符合条件
			cout << "银行家算法检查过后发现符合要求" << endl << endl;
			for (int i = 0; iallocation[i] += requestResource[i];
				q->need[i] -= requestResource[i];
			}
			cout << "下面进行安全性算法检查" << endl << endl;
			if (!securityAlgorithm(p))//当前系统处于不安全状态
				for (int i = 0; iallocation[i] -= requestResource[i];
					q->need[i] += requestResource[i];
				}
		}
		else//不符合条件
			cout << "银行家算法检查之后发现不符合要求" << endl << endl;
		cout << endl;
		string choose;
		cout << endl << "是否还有进程要申请资源,若是则输入YES，否则输入NO:";
		cin >> choose;
		if (choose == "NO")
			break;
	}
	q = NULL;
	delete q;
	return 0;
}

结果：