onethirtyfive / maxarea

code exercise

Exercise

=begin
You are given an integer array height of length n. There are n vertical lines drawn such that the two endpoints
of the ith line are (i, 0) and (i, height[i]).

Find two lines that together with the x-axis form a container, such that the container contains the most water.
Return the maximum amount of water a container can store. Notice that you may not slant the container.

Input: height = [1,8,6,2,5,4,8,3,7]
Output: 49
=end

# @param {Integer[]} height
# @return {Integer}
def max_area(height)

end

puts max_area([1,8,6,2,5,4,8,3,7])

Running and Details

Any 3.x version of Ruby will probably work. To run the tests you'll need rspec but ruby exercise.rb has no gem deps--it should just run.

Implementation ended up reasonably efficient (linear time and space complexity). Feel free to fiddle with the inputs in exercise.rb, rerun, and see what you get.

Final code coverage report (HTML) available at coverage.tgz.

Here is the output, if you're in a hurry.

Commit Play-by-Play

#1: Ad hoc devenv for exercise (no code changes)

6397aa9

I love the Nix Package Manager, but tl;dr: I made a little maxarea devenv which would install identically on any computer which:

1. has Nix installed,
2. enters this directory and types nix-shell

Like so:

maxarea on  main [?] via 💎 v2.6.10 took 1m21s
❯ ruby --version
ruby 2.6.10p210 (2022-04-12 revision 67958) [universal.arm64e-darwin22]

maxarea on  main [?] via 💎 v2.6.10
❯ nix-shell

[nix-shell:~/Code/maxarea]$ ruby --version
ruby 3.3.0preview2 (2023-09-14 master e50fcca9a7) [arm64-darwin22]

[nix-shell:~/Code/maxarea]$ gem list --local

*** LOCAL GEMS ***

[snip]
rspec (3.12.0)
rspec-core (3.12.2)
rspec-expectations (3.12.3)
rspec-mocks (3.12.6)
rspec-support (3.12.1)
[snip]

#2: exercise implementation

d333e79

It's pretty straightforward:

• demo: ruby exercise.rb, requries no dependencies
• lib/area.rb implements exercise support code
• spec/lib/area_spec.rb tests the exercise support code