batman, Java - rextester

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//'main' method must be in a class 'Rextester'.
//openjdk version '11.0.5'

import java.util.*;
import java.lang.*;
//import java.util.Stack;
class Rextester
{  
    public static int batman(int a[][], int p)
    {
        int z;
        Stack<Integer> s = new Stack<>();
        for(int i=0;i<p;i++)
            s.push(i);
        
      
       int x,y;
    
        while(s.size() > 1)
        {
              x=s.pop(); 
              y=s.pop();
            
          if(a[x][y]==1)
            s.push(y);
             
           else
             s.push(x);
             
        }
        if(s.empty())
            return -1;
        
        z=s.pop();
      // System.out.println(z);
        
      /*  if(a[z][y]==1)
            z=y;
        if(a[z][x]==1)
            z=x;*/
        
        for(int i=0;i<p;i++)
        {
           if( i!=z && ( (a[z][i] == 1) || a[i][z] == 0 ) )
               return -1;
        }
      return z;
    }
    public static void main(String args[])
    {
         Scanner sc=new Scanner(System.in);
         int p=sc.nextInt();
         int a[][]=new int[p][p];
        for(int i=0;i<p;i++)
            for(int j=0;j<p;j++)
               a[i][j]=sc.nextInt();
            
          int answer=batman(a,p);
         System.out.println(answer);
    }
}

[ - ] Show input
Compilation time: 2.95 sec, absolute running time: 0.37 sec, cpu time: 0.32 sec, memory peak: 37 Mb, absolute service time: 3,94 sec