How to find maximum xor in a sub matrix?

Question

eg given 3 x 3 matrix

   1 2 3
   4 5 6
   7 8 9

has max xor value = 15 sub matrix

   2 
   5 
   8

tha

Answer 1

You can use https://en.wikipedia.org/wiki/Fenwick_tree for fast xor calculation and updates. Segment tree is another structure that can be used. It has similar characteristics but uses more memory. Both can be used for 1D array case as well.