Celebrity_Problem.java

import java.util.*;
class Celebrity_Problem
{
    int top=-1,topi=-1;
    int max=1000;
    int[] stack= new int[1000];
    int[][] Ar;
    void push(int x)
    {
        if(top==(max-1))
        {
            System.out.println("Stack Overflow");
        }
        else
        {
            stack[++top]=x;
        }
    }
    int pop()
    {
        int elem=stack[top--];
        return elem;
    }
    int assume()
    {
        return(stack[top]);
    }
    void main()
    {
        Scanner sc = new Scanner(System.in);
        Celebrity_Problem obj= new Celebrity_Problem();
        int i,j,topi=-1;
        int n=sc.nextInt();
        int[][] Ar=new int[n][n];
        for(i=0;i<n;i++)
        {
            for(j=0;j<n;j++)
            {
                Ar[i][j]=sc.nextInt();
            }
        }
        for(i=0;i<n;i++)
        {
            obj.push(i);
        }
        for(i=0;i<(n-1);i++)
        {
            int ele1 = obj.pop();
            int ele2 = obj.pop();
            if(Ar[ele1][ele2]==0)
            {
                obj.push(ele1);
            }
            else if(Ar[ele1][ele2]==1)
            {
                obj.push(ele2);
            }
        }
        int assumed= obj.assume();
        int found=1;
        for (i=0;i<n;i++)
        {
           if(Ar[assumed][i]!=0)
           {
               found=0;
               break;
            }
            if(i!=assumed && Ar[i][assumed]!=1)
            {
                found=0;
                break;
            }
        }
        if(found==0)
        {
            System.out.println("-1");
        }
        else
        {
            System.out.println(assumed);
        }
    }
}