wood burning stoves
The moose likes Programming Diversions and the fly likes find sub-matrix with the maximum sum Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login

Win a copy of OCA Java SE 8 Programmer I Study Guide this week in the OCAJP 8 forum!
JavaRanch » Java Forums » Other » Programming Diversions
Bookmark "find sub-matrix with the maximum sum" Watch "find sub-matrix with the maximum sum" New topic

find sub-matrix with the maximum sum

megha joshi
Ranch Hand

Joined: Feb 20, 2007
Posts: 206
given N x N matrix of positive and negetive intergers. Write some code
that finds the sub-matrix with teh maximum sum of its elements.

Any ideas?

Ryan McGuire
Ranch Hand

Joined: Feb 18, 2005
Posts: 1041
There's an obvious O(N^6) brute force algorithm.

For each combination of upper left and lower right corners { // O(N^4)
Calculate the sum; // O(N^2)
If the new sum is greater than old maximum, remember it.

A question very similar to this in one dimension has an O(N) solution. That makes me think there must be an O(N^2) one for this.
[ October 15, 2007: Message edited by: Ryan McGuire ]
I agree. Here's the link: http://aspose.com/file-tools
subject: find sub-matrix with the maximum sum
It's not a secret anymore!