title: rectangular matrix complexity
body: <p>I have to compute complexity of algorithm which searches an element in a rectangular matrix. It uses divide and conquer. For square matrix my time functions becomes a*T(n/b)+O(n^2). But for rectangular matrix I don't know how to denote the division if it has to be divided into 4 sub matrices. Will it be a*T(m*n/4) + O(n)?</p>