先来先服务(FCFS)算法

快期末了在复习操作系统，顺便把实验课上写的算法重新写一遍

先来先服务算法非常简单，当作业来了，先来先运行，后来的按到达时间的先后排在就绪队列上，每次取队首元素运行。

实验环境是WIN7 64位+Visual Studio 2015

//main.cpp#include "FCFS.h"int main(){std::vector<PCB> PCBList;//输入作业信息InputPCB(PCBList);//FCFS算法FCFS(PCBList);//显示结果show(PCBList);return 0;}//FCFS.h#ifndef FCFS_H_#define FCFS_H_#include <iostream>#include <iomanip>#include <vector>#include <queue>//作业结构体typedef struct PCB{int ID;//标识符int ComeTime;//到达时间int ServerTime;//服务时间int FinishTime;//完成时间int TurnoverTime;//周转时间double WeightedTurnoverTime;//带权周转时间}PCB;/*函数功能：输入作业信息参数说明：PCBListstd::vector<PCB>&PCB链*/void InputPCB(std::vector<PCB> &PCBList);/*函数功能：FCFS算法参数说明：PCBListstd::vector<PCB>&PCB链*/void FCFS(std::vector<PCB> &PCBList);/*函数功能：显示结果参数说明：PCBListstd::vector<PCB>&PCB链*/void show(std::vector<PCB> &PCBList);/*函数功能：比较函数，用于sort()，按ComeTime升序排列参数说明：p1const PCB&PCBp2const PCB&PCB*/bool cmp(const PCB &p1, const PCB &p2);#endif//FCFS.cpp#include "FCFS.h"void InputPCB(std::vector<PCB> &PCBList){do {PCB temp;std::cout << "输入标识符: ";std::cin >> temp.ID;std::cout << "输入到达时间: ";std::cin >> temp.ComeTime;std::cout << "输入服务时间: ";std::cin >> temp.ServerTime;PCBList.push_back(temp);std::cout << "继续输入？Y/N: ";char ans;std::cin >> ans;if ('Y' == ans || 'y' == ans)continue;elsebreak;} while (true);}void FCFS(std::vector<PCB> &PCBList){std::sort(PCBList.begin(), PCBList.end(), cmp);//按升序排列ComeTimeint FinishTime = -1;//上一个作业的完成时间for (std::vector<PCB>::iterator it = PCBList.begin(); it < PCBList.end(); ++it){if ((*it).ComeTime < FinishTime)//作业到达时，上一个作业还没有结束(*it).FinishTime = (*(it - 1)).FinishTime + (*it).ServerTime;else(*it).FinishTime = (*it).ComeTime + (*it).ServerTime;(*it).TurnoverTime = (*it).FinishTime - (*it).ComeTime;(*it).WeightedTurnoverTime = (double)(*it).TurnoverTime / (*it).ServerTime;FinishTime = (*it).FinishTime;}}void show(std::vector<PCB> &PCBList){int SumTurnoverTime = 0;double SumWeightedTurnoverTime = 0;std::cout.setf(std::ios::left);std::cout << std::setw(20) << "标识符";for (std::vector<PCB>::iterator it = PCBList.begin(); it < PCBList.end(); ++it)std::cout << std::setw(5) << (*it).ID;std::cout << std::endl;std::cout << std::setw(20) << "到达时间";for (std::vector<PCB>::iterator it = PCBList.begin(); it < PCBList.end(); ++it)std::cout << std::setw(5) << (*it).ComeTime;std::cout << std::endl;std::cout << std::setw(20) << "服务时间";for (std::vector<PCB>::iterator it = PCBList.begin(); it < PCBList.end(); ++it)std::cout << std::setw(5) << (*it).ServerTime;std::cout << std::endl;std::cout << std::setw(20) << "完成时间";for (std::vector<PCB>::iterator it = PCBList.begin(); it < PCBList.end(); ++it)std::cout << std::setw(5) << (*it).FinishTime;std::cout << std::endl;std::cout << std::setw(20) << "周转时间";for (std::vector<PCB>::iterator it = PCBList.begin(); it < PCBList.end(); ++it){std::cout << std::setw(5) << (*it).TurnoverTime;SumTurnoverTime += (*it).TurnoverTime;;}std::cout << std::endl;std::cout << std::setw(20) << "带权周转时间";for (std::vector<PCB>::iterator it = PCBList.begin(); it < PCBList.end(); ++it){std::cout << std::setw(5) << (*it).WeightedTurnoverTime;SumWeightedTurnoverTime += (*it).WeightedTurnoverTime;;}std::cout << std::endl;std::cout << "平均周转时间: " << (double)SumTurnoverTime / PCBList.size() << std::endl;std::cout << "平均带权周转时间: " << SumWeightedTurnoverTime / PCBList.size() << std::endl;}bool cmp(const PCB &p1, const PCB &p2){return p1.ComeTime < p2.ComeTime;}