Problem 55220. Matrix Quadrants

Created by Renee Coetsee

Solve Later

Write a function that takes N as the input, and outputs a matrix whose upper-left (NxN) quadrant contains all ones, the lower-right (NxN) quadrant contains all N's, and zeros everywhere else. For example, if N = 3: 

Solve

Solution Stats

1552 Solutions
824 Solvers

Last Solution submitted on Oct 25, 2025

Last 200 Solutions

Problem Comments

5 Comments

5 Comments

Show 2 older comments

Aidan Judge on 29 Nov 2022

Good problem!

Andreea on 16 Jan 2023

function M = foursquare(N)
M = zeros(2*N);
for i=1:length(M)/2
for j=1:length(M)/2
M(i,j)=1;
j=j+1;
end
i=i+1;
end
for i=(length(M)/2)+1:length(M)
for j=(length(M)/2)+1:length(M)
M(i,j)=3;
j=j+1;
end
i=i+1;
end
end
Just wrote that program that gives me the right solution but I don't understand why it won't work.Any suggestions?

Christian Schröder on 17 Jan 2023

@Andreea you're hard-coding the value 3 on the twelfth line; the problem description says that the lower-left quadrant should contain N's instead.

Kshitij Patki on 20 Mar 2025

good one

David on 24 Oct 2025 at 23:36

N=3
A=ones(3)
B=zeros(3)
C=N*ones(3)
M=([A B;B C])

I'm just starting out self learning and to my understanding this code answers the question since i made N an input but it says i did it wrong. i guess i have to use this 'foursquare' function (only seeing it for the first time now). can someone please explain what the function does?

Solution Comments

Show comments

Problem Recent Solvers824

Problem Tags

Community Treasure Hunt

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

Start Hunting!

Problem 55220. Matrix Quadrants

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers824

Suggested Problems

More from this Author10

Problem Tags

Community Treasure Hunt

Problem 55220. Matrix Quadrants

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers824

Suggested Problems

More from this Author10

Problem Tags

Community Treasure Hunt

Players