How do I search for a number in a 2d array sorted left to right and top to bottom?

Question

I was recently given this interview question and I\'m curious what a good solution to it would be.

Say I\'m given a 2d array where all the numbers i

Answer 1

A. Do a binary search on those lines where the target number might be on.

B. Make it a graph : Look for the number by taking always the smallest unvisited neighbour node and backtracking when a too big number is found