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#include <stdio.h>
#include <stdlib.h>

typedef enum pstate
{
    READY,
    RUNNING,
    FINISHED
} pstate;

typedef struct PCB
{
    
    int pid;
    
    pstate state;
    
    int arrivetime;
    
    int runtime;
    
    int prior;
    
    struct PCB *next;
} PCB;

int main()
{
    srand(20);
    
    int pian = 3;
    
    int p_num = 5;
    
    int pid_count = 1;
    PCB *head = (PCB *)malloc(sizeof(PCB));
    head->pid = -1;
    head->prior = -1;
    head->next = NULL;
    PCB *current = head;
    while (p_num > 0)
    {
        PCB *new_pcb = (PCB *)malloc(sizeof(PCB));

        new_pcb->pid = pid_count;
        pid_count++;
        new_pcb->state = READY;
        new_pcb->arrivetime = rand() % 20;
        new_pcb->runtime = rand() % 10 + 1;
        new_pcb->prior = rand() % 10 + 1;
        new_pcb->next = NULL;

        current->next = new_pcb;
        current = current->next;
        p_num--;
    }

    
    int now_time = 0;
    while (1)
    {
        PCB *ahead_current = head;
        current = head->next;
        
        if (current == NULL)
        {
            break;
        }

        
        PCB *ahead_pcb = NULL;
        PCB *max_prior_pcb = head;
        while (current != NULL)
        {
            if (current->arrivetime <= now_time && current->state == READY && current->prior >= max_prior_pcb->prior)
            {
                max_prior_pcb = current;
                ahead_pcb = ahead_current;
            }
            ahead_current = current;
            current = current->next;
        }

        
        if (max_prior_pcb->pid < 0)
        {
            printf("当前时间为:%d 等待程序到达中……\n",now_time);
            now_time += 1;
            continue;
        }

        
        
        max_prior_pcb->state = RUNNING;
        printf("当前执行程序：PID:%d 到达时间:%d 剩余时间:%d 优先级:%d\n", max_prior_pcb->pid, max_prior_pcb->arrivetime, max_prior_pcb->runtime, max_prior_pcb->prior);
        
        if (max_prior_pcb->runtime <= pian)
        {
            
            now_time += max_prior_pcb->runtime;
            
            max_prior_pcb->runtime = 0;
            
            max_prior_pcb->state = FINISHED;
            printf("当前程序执行完成：PID:%d 剩余时间:%d 状态:已完成 当前时间:%d\n\n", max_prior_pcb->pid, max_prior_pcb->runtime,now_time);
            
            ahead_pcb->next = max_prior_pcb->next;
            free(max_prior_pcb);
        }
        else
        {
            
            now_time += pian;
            
            max_prior_pcb->runtime = (max_prior_pcb->runtime - pian);
            
            max_prior_pcb->state = READY;
            printf("当前程序时间片已耗费完：PID:%d 剩余时间:%d 状态:等待继续 当前时间:%d\n\n", max_prior_pcb->pid, max_prior_pcb->runtime,now_time);
        }
    }
    printf("所有程序已执行完毕：花费时间：%d\n", now_time);
}