Past exam of the year 1 of the computer science course of the University of Oxford / 2015 / Imperative programming / 2 / c / Solution

Write $v=f[0,N-1]$, assuming $M,N>0$. By monotonicity, $v$ is at least every value in the first row and at most every value in the last column. HenceThe same observation applies to the top-right corner of any remaining rectangular subarray of this monotone matrix.