Problem 512. Spot the rectangle

Created by Ned Gulley

Solve Later

This problem is related to the 17x17 challenge. Given a matrix filled with ones and zeros, determine whether or not any rectangles are present. A rectangle is a formed whenever four ones appear in the corners of a rectangular region of the matrix.
Examples:
 Input  a = [ 1 0 0 0 0
              0 0 0 1 0
              0 0 0 0 1
              0 0 0 0 1
              0 0 1 0 0 ]
 Output tf is false
You can't form any rectangles here.
 Input  a = [ 1 0 1 0
              0 0 1 0
              1 0 1 0
              0 0 1 1 ]
 Output tf is true
There is a rectangle: a([1 3],[1 3]) is [1 1; 1 1]

Solve

Solution Stats

660 Solutions
110 Solvers

Last Solution submitted on Dec 06, 2023

Last 200 Solutions

Problem Comments

3 Comments

3 Comments

rifat on 15 Jun 2014

test cases imply that the question title should be "spot the square"

Ned Gulley on 14 Jan 2015

I added a rectangular (non-square) test case. Thanks for the note.

Christian Schröder on 28 Sep 2022

Could you add

a = ones(3) - eye(3)

to the test suite?

Solution Comments

Show comments

Problem Recent Solvers110

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 512. Spot the rectangle

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers110

Suggested Problems

More from this Author50

Problem Tags

Community Treasure Hunt

Problem 512. Spot the rectangle

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers110

Suggested Problems

More from this Author50

Problem Tags

Community Treasure Hunt

Players