Implement the FCFS(First Come First Served) algorithm for CPU scheduling.


Input
The name of input file is “fcfs.inp.”
In the first line, an integer n, the number of processes is given. In each line of the following n lines, the information of each process is given as following:
PID(Process Identification Number), Arrival Time, CPU burst

PID, Arrival Time and CPU burst are given as integers and each is separated by blank (the number of blank characters is one or more). If two or more processes arrive at the ready queue at the same time, process with smaller PID will get CPU first. PIDs are between 0 and n-1 and the maximum value of n is 50.


Output
Your program is to write to a file named “fcfs.out.”
Calculate the waiting time for each process and print the sum of them.


The following shows sample input and output.

Sample Input
4
3 7 6
1 5 7
0 0 13
2 11 18

Output
36

#include<fstream>

using namespace std;



int nJobs,pid[10], burstTime[10],arrivalTime[10];

int burstTimeTemp=0;

int waitingTime=0;

void calculateFCFS()

{

 for(int i=1;i<nJobs

 {

 if(pid[i]>pid[nJobs-i])

 {

 arrivalTime[i]=arrivalTime[nJobs-i];

 burstTime[i]=burstTime[nJobs-i];

 }

 else 

 {

 burstTimeTemp=burstTime[i]+burstTimeTemp;

 waitingTime=waitingTime+burstTimeTemp;

 }

 ++i;

 }

}



int main()

{

 int linecount=0;

 freopen("fcfs.inp","r",stdin);

 freopen("fcfs.out","w",stdout);

 scanf("%d",&nJobs);

 for(linecount=2;linecount<nJobs

 {

 

 scanf("%d",&pid[linecount]);

 scanf("%d",&arrivalTime[linecount]); 

 scanf("%d",&burstTime[linecount]);

 ++linecount;

 

 

 }

 calculateFCFS();



 printf("%d",waitingTime);

 fclose(stdin);

 fclose(stdout);

 

 return 0;

}