# Demo entry 6338285

SJF

Submitted by anonymous on Dec 11, 2016 at 09:53
Language: C++. Code size: 3.3 kB.

//调度算法的模拟
//1.SJF 短作业优先算法

#include<stdio.h>
#include <malloc.h>
#include <string>
#include <string.h>
#include <iostream>
using namespace std;

#define N 5  //假设5个进程

struct PCB {
string name;//进程name
int reachTime;//标志进程到达时间
int needTime;//进程所需的时间
bool state;
/*进程的状态，false表示挂起，true表示激活*/
int alltime;//总共所用的时间，即周转时间
bool over;   //进程的状态，true表示结束
bool isrunning;
}P[5];  //声明5个进程
void init();
void processSchedule();
void printPCB(PCB P);

int arr[10];  //队列存放可以运行但是没有被调度的进程
int Size = 0; //队列的长度
int RunningP = -1; //当前运行进程编号

void Sort(int a[], int Size);

int main() {
init();  //初始化这五个进程
processSchedule();//进程调度

cout << "*-----------------------输出部分------------------------*" << endl;
cout << "进程名称" << "\t" << "到达时间" << "\t" << "所需时间" << "\t" << "周转时间" << endl;
for (int i = 0; i < 5; i++) {
printPCB(P[i]); //打印进程信息
}

return 0;
}

void init() {

cout << "*------------------短作业优先算法-------------------*" << endl;
for (int i = 0; i<N; i++) {
cout << "输入进程" << i + 1 << "名称，到达时间，所需时间（用空格键隔开）：" << endl;
cin >> P[i].name >> P[i].reachTime >> P[i].needTime;
}
for (int i = 0; i<N; i++) {
P[i].state = 0;
P[i].alltime = 0;
P[i].isrunning = 0;
P[i].over = 0;
}
/*P[0].name = "P1";
P[0].reachTime = 0;
P[0].needTime = 4;
P[0].state = 0;
P[0].alltime = 0;
P[0].over = 0;
P[0].isrunning = 0;

P[1].name = "P2";
P[1].reachTime = 1;
P[1].needTime = 3;
P[1].state = 0;
P[1].alltime = 0;
P[1].over = 0;
P[1].isrunning = 0;

P[2].name = "P3";
P[2].reachTime = 2;
P[2].needTime = 5;
P[2].state = 0;
P[2].alltime = 0;
P[2].over = 0;
P[2].isrunning = 0;

P[3].name = "P4";
P[3].reachTime = 3;
P[3].needTime = 2;
P[3].state = 0;
P[3].alltime = 0;
P[3].over = 0;
P[3].isrunning = 0;

P[4].name = "P5";
P[4].reachTime = 4;
P[4].needTime = 4;
P[4].state = 0;
P[4].alltime = 0;
P[4].over = 0;
P[4].isrunning = 0;*/
}

void printPCB(PCB P) {
cout << P.name << "\t\t" << P.reachTime << "\t\t" << P.needTime << "\t\t" << P.alltime << endl;
}

void setState(int all) { //找到该时刻到达的进程，并将它放入队列中
for (int i = 0; i < N; i++) {
if (P[i].reachTime == all) {
arr[Size] = i;  //放到队列的最后
P[i].state = 1;  //标志该进程状态激活
Size++;   //队列长度++
}
}
}

void Sort(int Size) {  //对队列中的进程按照执行需要的时间排序，从长到短
for (int i = 0; i < Size; i++) {
for (int j = i + 1; j < Size; j++) {
if (P[arr[i]].needTime < P[arr[j]].needTime) {  //短作业放最后
int tmp = arr[i];
arr[i] = arr[j];
arr[j] = tmp;
}
}
}
}

void processSchedule() {
int all = 0; //记录系统运行总时间

for (int n = 0; n < N; n++) { //五个进程
int time = 0;  //记录该进程执行时间
while (true) {

setState(all);
Sort(Size);
time++;
all++;
if (RunningP == -1) {  //如果没有进程在执行
if (Size > 0) {
RunningP = arr[Size - 1];//调入运行所需时间最短的进程，即队列中最后边的进程
Size--; //队列长度减一
}
}
if (RunningP != -1) { //如果有进程在运行
if (P[RunningP].needTime == time) {//如果该进程已经执行完成
P[RunningP].alltime = all - P[RunningP].reachTime;//计算该进程周转时间
RunningP = -1;//重新标记没有进程在运行
break;//跳出while
}
}
}
}
}

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