Connected Horses Problem

Kindly someone elaborate on the process in which input is taken in the following code?

Problem Statement :

import java.util.Scanner;
import java.io.*;
import java.util.*;
import java.math.*;
import java.lang.*;
import static java.lang.Math.*;
 
public class Check2 implements Runnable{
 
	static class InputReader
	{
		private InputStream stream;
		private byte[] buf = new byte[1024];
		private int curChar;
		private int numChars;
		private SpaceCharFilter filter;
		
		public InputReader(InputStream stream)
		{
			this.stream = stream;
		}
		
		public int read()
		{
			if (numChars==-1) 
				throw new InputMismatchException();
			
			if (curChar >= numChars)
			{
				curChar = 0;
				try 
				{
					numChars = stream.read(buf);
				}
				catch (IOException e)
				{
					throw new InputMismatchException();
				}
				
				if(numChars <= 0)				
					return -1;
			}
			return buf[curChar++];
		}
	 
		public String nextLine()
		{
			BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
			String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
		}
		public int nextInt()
		{
			int c = read();
			
			while(isSpaceChar(c)) 
				c = read();
			
			int sgn = 1;
			
			if (c == '-') 
			{
				sgn = -1;
				c = read();
			}
			
			int res = 0;
			do 
			{
				if(c<'0'||c>'9') 
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();\r
			}
			while (!isSpaceChar(c)); 
			
			return res * sgn;
		}
		
		public long nextLong() 
		{
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') 
			{
				sgn = -1;
				c = read();
			}
			long res = 0;
			
			do 
			{
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			}
			while (!isSpaceChar(c));
				return res * sgn;
		}
		
		public double nextDouble() 
		{
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') 
			{
				sgn = -1;
				c = read();
			}
			double res = 0;
			while (!isSpaceChar(c) && c != '.') 
			{
				if (c == 'e' || c == 'E')
					return res * Math.pow(10, nextInt());
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			}
			if (c == '.') 
			{
				c = read();
				double m = 1;
				while (!isSpaceChar(c)) 
				{
					if (c == 'e' || c == 'E')
						return res * Math.pow(10, nextInt());
					if (c < '0' || c > '9')
						throw new InputMismatchException();
					m /= 10;
					res += (c - '0') * m;
					c = read();
				}
			}
			return res * sgn;
		}
		
		public String readString() 
		{
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do 
			{
				res.appendCodePoint(c);
				c = read();
			} 
			while (!isSpaceChar(c));
			
			return res.toString();
		}
	 
		public boolean isSpaceChar(int c) 
		{
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '' || c == '\t' || c == -1;
		}
	 
		public String next() 
		{
			return readString();
		}
		
		public interface SpaceCharFilter 
		{
			public boolean isSpaceChar(int ch);
		}
	}


	static LinkedList <Integer> adj[];
    static int co=0,f=0;
    static int n,m;
	
    static void Check2(int n){
        adj=new LinkedList[n+1];
        for(int i=0;i<=n;i++){
            adj[i]=new LinkedList();
        }
        
    }
    static void add(int i,int j){
        
        adj[i].add(j);
        adj[j].add(i);
        
    }
	  public static void main(String[] args) throws Exception { 
    new Thread(null, new Check2(), "Check2", 1<<26).start();

  }
  public void run(){
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        //Scanner in=new Scanner(System.in);
    InputReader in=new InputReader(System.in);		
		PrintWriter w=new PrintWriter(System.out);
	
long mod=1000000007l;
		long fact[]=new long[1000001];
		fact[0]=1;
		fact[1]=1;
		for(int i=2;i<=1000000;i++)
		{
		    fact[i]=i*fact[i-1];
		    fact[i]%=mod;
		}
		
		int t=in.nextInt();
		while(t-->0){
		    
		    
		
		 n=in.nextInt();
		 m=in.nextInt();
		co=1;
		int q=in.nextInt();
		int a[][]=new int[n+1][m+1];
		
	//	Check2(n);
		for(int i=0;i<q;i++)
		{
		    int c=in.nextInt();
		    int d=in.nextInt();
		    a[c][d]=1;
		    
		  //  add(c,d);
		}
		
		
		int v[][]=new int[n+1][m+1];
		long ans=1;
	
		for(int i=1;i<=n;i++)
		{
		    for(int j=1;j<=m;j++){
		        
		        if(v[i][j]==0&&a[i][j]==1){
		            co=1;
		            dfs2(i,j,v,a);
		    //        w.println(co+" "+i+" "+j+"hiiiiiiiiiii");
		            ans=ans*fact[co];
		            ans%=mod;
		        }
		    }
		}
		w.println(ans);
		
		}
		
		
		
		
        w.close();
        
           
    }
    
    static void dfs(int i,int v[]){
        if(v[i]==1){
            return ;
        }
        else{
            
            v[i]=1;
            Iterator <Integer>p=adj[i].iterator();
            while(p.hasNext()){
                 Integer ne=p.next();
                
                    
                    
              dfs(ne,v);
     //          
       //        System.out.println(q+" "+i);
            //System.out.println(i+" "+max1+" "+max2);
            }
            
            
            
            
            
        }
        
        
    }
    
    
    static void dfs2(int i,int j,int v[][],int a[][])
    {
        
        v[i][j]=1;
        if(i<n-1&&j!=m&&a[i+2][j+1]==1&&v[i+2][j+1]==0)
        
        {
            co++;
            v[i+2][j+1]=1;
            dfs2(i+2,j+1,v,a);
        }
         if(i<n-1&&j!=0&&a[i+2][j-1]==1&&v[i+2][j-1]==0)
        
        {
            co++;
            v[i+2][j-1]=1;
            dfs2(i+2,j-1,v,a);
        }
        if(i>1&&j!=m&&a[i-2][j+1]==1&&v[i-2][j+1]==0)
        
        {
            co++;
            v[i-2][j+1]=1;
            dfs2(i-2,j+1,v,a);
        }
       
        if(i>1&&j!=0&&a[i-2][j-1]==1&&v[i-2][j-1]==0)
        
        {
            co++;
            v[i-2][j-1]=1;
            dfs2(i-2,j-1,v,a);
        }
        if(i!=n&&j>=2&&a[i+1][j-2]==1&&v[i+1][j-2]==0)
        
        {
            co++;
            v[i+1][j-2]=1;
            dfs2(i+1,j-2,v,a);
        }
       
        if(i!=n&&j<m-1&&a[i+1][j+2]==1&&v[i+1][j+2]==0)
        
        {
            co++;
            v[i+1][j+2]=1;
            dfs2(i+1,j+2,v,a);
        }
        if(i>=1&&j<m-1&&a[i-1][j+2]==1&&v[i-1][j+2]==0)
        
        {
        //    System.out.println(i+" "+j);
            co++;
            v[i-1][j+2]=1;
            dfs2(i-1,j+2,v,a);
        }
       
        if(i>=1&&j>=2&&a[i-1][j-2]==1&&v[i-1][j-2]==0)
        
        {
            co++;
            v[i-1][j-2]=1;
            dfs2(i-1,j-2,v,a);
        }
       
        
        
    }
    
    
    static class node{
        
        int y;
        int val;
        
        node(int a,int b){
            
            y=a;
            val=b;
            
        }
        
        
    }
    
}