//**************************************
// Name: Priority Scheduling Algorithm
// Description:This code solves the problem of priority scheduling algorithm of operating systems. I guessed that no two processes may have same priority. A gantt chart has been shown for easy understanding of the outcomes. Any improvement on this code is highly appreciable.
// By: Mahmud_Hasan
//
// Inputs:It asks for no of processes and their burst times along with their priorities.
//
// Returns:Nothing
//
// Side Effects:Nothing
//
//This code is copyrighted and has// limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=13081&lngWId=3//for details.//**************************************

#include<iostream.h>
void main()
{
	int priority[20],btime[20],wtime[20],process[20],priority_2[20], sort_p[20],btime2[20];
	int n,i,j;
	cout<<"Please enter the number of processes:";
	cin>>n;
	cout<<endl;
	for(i=0;i<n;i++)
	{
		cout<<"Enter Busrt Time for Process P"<<i+1<<":";
		cin>>btime[i];
		cout<<"Enter Priority for Process P"<<i+1<<":";
		cin>>priority[i];
		cout<<endl;
		priority_2[i]=priority[i];
		process[i]=i+1;
	}
	//sorting priority
	for(i=0;i<n-1;i++)
	{
		for(j=n-1;i<j;j--)
		{
			if(priority[j]<priority[j-1])
			{
				double t;
				t=priority[j];
				priority[j]=priority[j-1];
				priority[j-1]=t;
			}
		}
	}
	//sorting processes according to priority
	for(i=0;i<n;i++)
	{
		for(j=0;j<n;j++)
		{
			if(priority[i]==priority_2[j])
			{
				sort_p[i]=j+1;
				btime2[i]=btime[j];
			}
		}
	}
	cout<<endl<<"Process ---> Burst Time"<<endl<<endl;
	for(i=0;i<n;i++)
	{
		cout<<""<<sort_p[i]<<"\t--->"<<"\t "<<btime2[i]<<endl;
	}
	//finding waiting time
	cout<<"\n\n\n\t\t\t::Time Calculation::\n\n\n";
	int sum=0;
	for(i=0;i<n;i++)
	{
		if(i==0)
			wtime[i]=0;
		else
		{
			sum+=btime2[i-1];
			wtime[i]=sum;
		}
		cout<<"waiting time for process p"<<sort_p[i]<<": "<<wtime[i]<<endl;
	}
	wtime[i]=sum+btime2[i-1];
	sum=0;
	for(i=0;i<n;i++)
	{
		sum+=wtime[i];
	}
	double avg=(double)sum/(double)n;
	cout<<endl<<endl<<"Average Waiting Time: "<<avg<<" milliseconds.";
	//drawing gantt chart....
	cout<<"\n\n\n\t\t\t::GANTT CHART::\n\n";
	cout<<endl<<"---------------------------------------------------------------------------"<<endl;
	for(i=0;i<n;i++)
		cout<<"|\tP"<<sort_p[i]<<"\t";
	//cout<<"|";
	cout<<endl<<"---------------------------------------------------------------------------"<<endl;
	cout<<endl;
	for(i=0;i<=n;i++)
	{
		if(i==n-1)
			cout<<wtime[i]<<"\t";
		else
			cout<<wtime[i]<<"\t\t";
	}
	cout<<endl<<"---------------------------------------------------------------------------"<<endl;
	cout<<endl;
}
/*
sample input:
5
10
3
1
1
2
4
1
5
5
2
*/