public void zero_old(int[][] matrix) {
		if(matrix == null)
			return;
		int m = matrix.length;
		if(m == 0)
			return;
		int n = matrix[0].length;
		boolean[] row_zero = new boolean[m];
		boolean[] col_zero = new boolean[n];
		for(int i = 0; i < m; i++)
			for(int j = 0; j < n; j++)
			{
				if(matrix[i][j] == 0)
				{
					row_zero[i] = true;
					col_zero[j] = true;
				}
			}
		for(int i = 0; i < m; i++)
			for(int j = 0; j < n; j++)
			{
				if(row_zero[i] || col_zero[j])
					matrix[i][j] = 0;
			}
	}