CareerCup

//I didn't do any input parsing, this is what comes after.
public class Point 
{
	int row;
	int col;
	
	public Point(int r,int c)
	{
		row=r;
		col=c;
	}
	
	public int hashCode()
	{
		int[] vals={row,col};
		return Arrays.hashCode(vals);
	}
	
	public boolean equals(Object obj)
	{
		if(obj==null || !obj instanceof Point)
		{
			return false;
		}
		Point p=(Point)obj;
		return hashCode()==p.hashCode();
	}
}

private void bfs(int[][] m,Point p)
{
	int level=0;
	Deque<Point> q=new LinkedList<Point>();
	HashSet<Point> set=new HashSet<Point>();
	set.add(p);
	q.addFirst(p);
	q.addLast(null);
	while(!q.isEmpty())
	{
		level++;
		while(q.peekFirst()!=null)
		{
			Point curr=q.removeFirst();
			Point[] dirs={new Point(-1,0),new Point(1,0),new Point(0,-1),new Point(0,1)};
			for(Point x:dirs)
			{
				Point next=new Point(curr.row+x.row,curr.col+x.col);
				if(isValid(next,set,matrix) && m[next.row][next.col]>level)
				{
					m[next.row][next.col]=level;
					q.addLast(next);
					
				}
			}
		}
		q.removeFirst();
		q.addLast(null;)
		
	}
	
}

private boolean isValid(Point p, HashSet<Point> set, int[][] m)
{
	return(!set.contains(p) && (p.row>=0 && p.row<m.length) && (p.col>=0 && p.col<m[0].length));
}

public int[][] modifyArray(int[][] matrix)
{
	if(matrix==null||matrix.length==0)
	{
		return null;
	}
	
	ArrayList<Point> ls=getZeros(matrix);
	for(int i=0;i<matrix.length;i++)
	{
		for(int j=0;j<matrix[0].length;j++)
		{
			if(m[i][j]!=0)
			{
				m[i][j]=Integer.MAX_VALUE;
			}
		}
	}
	
	for(Point p:ls)
	{
		bfs(matrix,p);
	}
}

//Time Complexity: O(NMP) where N is number of rows, M is the number of columns and //P is the number positions with zero. Space: O(NM)