时间片轮询算法

时间片轮询算法

一.代码

#define _CRT_SECURE_NO_WARNINGS 
#include<stdio.h>
#include<stdlib.h>
#define n 10//进程名最大长度
#define MAX 5//进程数
//定义进程类型
typedef struct pcb {
	char name[n];
	struct pcb* next;
	int arrivaltime;
	int runtime;
	int flag;
}PCB;

int timecount = 0;
PCB progress[MAX];
PCB* run = NULL;
//定义队列
typedef struct {
	PCB* front;
	PCB* rear;
}LinkQueen;

LinkQueen* CreateQueen(LinkQueen* q) {
	q = (LinkQueen*)malloc(sizeof(LinkQueen));
	q->front = q->rear = NULL;
	return q;
}

LinkQueen* DestroyQueen(LinkQueen* q) {
	PCB* pre = q->front, * p;
	if (pre != NULL) {
		p = pre->next;
		while (p != NULL) {
			free(pre);
			pre = p; p = p->next;
		}
		free(pre);
	}
	free(q);
	return q;
}

int QueenEmpty(LinkQueen* q) {
	if (q->rear == NULL)
		return 1;
	return 0;
}

LinkQueen* enQueen(LinkQueen* q, PCB* e) {
	PCB* p = NULL;
	p = (PCB*)malloc(sizeof(PCB));
	p->arrivaltime = e->arrivaltime;
	p->flag = e->flag;
	for (int i = 0; p->name[i] != '\0'; i++)
		p->name[i] = e->name[i];
	p->runtime = e->runtime;
	p->next = NULL;
	if (q->rear == NULL) {
		q->front = p;
		q->rear = p;
	}
	else {
		q->rear->next = p;
		q->rear = p;
	}
	return q;
}
//输入函数
void input() {
	for (int i = 0; i < MAX; i++) {
		scanf("%s", &progress[i].name);
		scanf("%d %d", &progress[i].arrivaltime, &progress[i].runtime);
		progress[i].flag = 0;
		progress[i].next = NULL;
	}
}

void Print() {
	printf("当前时间片: %d到%d\t", timecount, timecount + 1);
	printf("运行当前进程：%s\t", run->name);
	printf("当前进程剩余时间：%d\t", run->runtime);
	printf("此时状态flag=%d\t\n", run->flag);
}
//得到最晚到达的时间
int getlatest() {
	int max = 0;
	for (int i = 0; i < MAX; i++)
		if (progress[i].arrivaltime > max)
			max = progress[i].arrivaltime;
	return max;
}
//得到结束时间
int getendtime() {
	int sum = 0;
	for (int i = 0; i < MAX; i++)
		sum += progress[i].runtime;
	return sum;
}

LinkQueen* isarrival(LinkQueen* q) {
	for (int i = 0; i < MAX; i++)
		if (progress[i].arrivaltime == timecount)
			q = enQueen(q, &progress[i]);
	return q;
}

void isterminate() {
	if (run->runtime == 0)
		run->flag = -1;
}
//进程运行操作
LinkQueen* running(LinkQueen* q) {
	if (run == NULL) {
		if (QueenEmpty(q))
			return q;
		if (q->front == q->rear) {
			run = q->front;
			q->front = q->rear = NULL;
			run->runtime--;
			isterminate();
			Print();
		}
		else {
			run = q->front;
			q->front = q->front->next;
			run->runtime--;
			isterminate();
			Print();
		}
	}
	else {
		if (run->flag != -1) {
			if (QueenEmpty(q)) {
				run->runtime--;
				isterminate();
				Print();
			}
			else {
				q->rear->next = run;
				q->rear = run;
				run = q->front;
				q->front = q->front->next;
				run->runtime--;
				isterminate();
				Print();
			}
		}
		else {
			free(run);
			run = NULL;
			if (QueenEmpty(q))
				return q;
			if (q->front == q->rear) {
				run = q->front;
				q->front = q->rear = NULL;
				run->runtime--;
				isterminate();
				Print();
			}
			else {
				run = q->front;
				q->front = q->front->next;
				run->runtime--;
				isterminate();
				Print();
			}
		}
	}
	return q;
}
//CPU操作
void CPU(LinkQueen* q) {
	while (1) {
		if (timecount <= getlatest()) {
			q = isarrival(q);
			q = running(q);
			timecount++;
		}
		else {
			if (timecount >= getendtime()) {
				printf("over!\n");
				q = DestroyQueen(q);
				break;
			}
			q = running(q);
			timecount++;
		}
	}
}

int main() {
	LinkQueen* q = NULL;
	q = CreateQueen(q);
	input();
	CPU(q);
}

二.思路

三.运行结果