DataStructuresPracticeCodes/MST Prims algorithm.cpp at master · Roshan13046/DataStructuresPracticeCodes · GitHub

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#include<stdint.h>
#include<iostream>
using namespace std;
#define  n 7

#define x INT_MAX
 int a[n+1][n+1]=
	{ {x,x,x,x,x,x,x,x,},
	  {x,x,25,x,x,x,5,x },
	  {x,25,x,12,x,x,x,10},
	  {x,x,12,x,8,x,x,x},
	  {x,x,x,8,x,16,x,14},
	  {x,x,x,x,16,x,20,18},
	  {x,5,x,x,x,20,x,x},
	  {x,x,10,x,14,18,x,x}
	};


class mini
{
	public:
			int i,j,data;

			mini()
			{
				i=j=-1;
				data=1000;
			}

};

  mini min_cost()
 {
	int i,j;
	mini m;

	for(i=1;i<=n;i++)
	{
		for(j=i;j<=n;j++)
		{
			if(a[i][j] < m.data)
			{
				m.data =a[i][j];
				m.i=i;
				m.j=j;
			}
		}
	}

	return m;
}


 int near[n+1]={-1,-1,-1,-1,-1,-1,-1,-1};        //initializing to -1
mini near_cost(int p,int q)
{
  //update nearest array
	near[p]=near[q]=0;
	int vertex;
	for(int k=1;k<=n ;k++)
	{
		if(near[k]==0 );

		else if(near[k] == -1)
		{
			vertex=a[k][p]<a[k][q]?p:q	;
			near[k]=vertex;
		}
		else
		{
			//cout<<k<<" "<<near[k]<<" ;";
			vertex=a[k][p]<a[k][q]?p:q	;

		near[k]= a[k][near[k]] < a[k][vertex] ? near[k] : vertex;  //update statements
		}
	}

	///////////////////////////////////
   /*
	cout<<"check near values :";
	for(int i=0;i<=n;i++)
		cout<<near[i]<<" ";
	cout<<endl;
	*/
	////////////////////////////
	mini m;

	m.data=a[1][near[1]];
	m.i=1;
	m.j=near[1];

	for(int i=2;i<=n;i++)
	{
		if(a[i][near[i]]<m.data)
		{
			m.data =a[i][near[i]];
			m.i=i;
			m.j=near[i];
		}
	}
	return m;
}


int find_cost(int t[][n-1])
{
	int sum = 0;

	int i,j;

/*	for(i=0;i<n+1;i++)
		{
		 for(j=0;j<n+1;j++ )
			cout<<a[i][j]<<" ";
		cout<<endl;
	}
*/
	int p,q;

	for(int i=0;i<n-1;i++)
	{
		p=t[0][i];
		q= t[1][i];
		sum = sum + a[ p ] [q ];
	}
	return sum;
}


void prims()
{
	int t[2][n-1]={0};
	int k;

	mini m;
	m= min_cost();
	t[0][0]=m.i;
	t[1][0]=m.j;

	for(k=0;k<n-2;k++)
	{
		m=near_cost(t[0][k],t[1][k]);

		//cout<<"check :"<<m.i<<" "<<m.j;


		t[0][k+1]=m.i;
		t[1][k+1]=m.j;
	}

	cout<<" \n The path is : "<<endl;
	for(int i=0;i<n-1;i++)
	{
		cout<<" ( "<<t[0][i]<<" , "<<t[1][i]<<")"<<endl;
	}

	cout<<"\n The  cost of MST is :"<<find_cost(t);


}


main()
{


	prims();


}