Leftmost Column with at Least a One
 A binary matrix means that all elements are  0  or  1 . For each  individual  row of the matrix, this row is sorted in non-decreasing order.   Given a row-sorted binary matrix binaryMatrix, return leftmost column index(0-indexed) with at least a  1  in it. If such index doesn't exist, return -1 .   You can't access the Binary Matrix directly.   You may only access the matrix using a  BinaryMatrix  interface:   BinaryMatrix.get(x, y)  returns the element of the matrix at index (x, y)  (0-indexed).  BinaryMatrix.dimensions()  returns a list of 2 elements  [n, m] , which means the matrix is n * m .   Submissions making more than 1000  calls to  BinaryMatrix.get  will be judged Wrong Answer .  Also, any solutions that attempt to circumvent the judge will result in disqualification.  For custom testing purposes you're given the binary matrix mat  as input in the following four ...