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# fsalvini's solution

## to Rectangles in the OCaml Track

Published at Mar 16 2019 · 0 comments
Instructions
Test suite
Solution

#### Note:

This exercise has changed since this solution was written.

Count the rectangles in an ASCII diagram like the one below.

``````   +--+
++  |
+-++--+
|  |  |
+--+--+
``````

The above diagram contains 6 rectangles:

``````

+-----+
|     |
+-----+
``````
``````   +--+
|  |
|  |
|  |
+--+
``````
``````   +--+
|  |
+--+

``````
``````

+--+
|  |
+--+
``````
``````

+--+
|  |
+--+
``````
``````
++
++

``````

You may assume that the input is always a proper rectangle (i.e. the length of every line equals the length of the first line).

## Getting Started

For installation and learning resources, refer to the exercism help page.

## Installation

To work on the exercises, you will need `Opam` and `Base`. Consult opam website for instructions on how to install `opam` for your OS. Once `opam` is installed open a terminal window and run the following command to install base:

``````opam install base
``````

To run the tests you will need `OUnit`. Install it using `opam`:

``````opam install ounit
``````

## Running Tests

A Makefile is provided with a default target to compile your solution and run the tests. At the command line, type:

``````make
``````

## Interactive Shell

`utop` is a command line program which allows you to run Ocaml code interactively. The easiest way to install it is via opam:

``````opam install utop
``````

Consult utop for more detail.

## Feedback, Issues, Pull Requests

The exercism/ocaml repository on GitHub is the home for all of the Ocaml exercises.

If you have feedback about an exercise, or want to help implementing a new one, head over there and create an issue. We'll do our best to help you!

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### test.ml

``````open OUnit2
open Rectangles

let ae exp got _test_ctxt = assert_equal exp got ~printer:string_of_int

let tests = [
"no rows" >::
ae 0 (count_rectangles [||]);
"no columns" >::
ae 0 (count_rectangles [|""|]);
"no rectangles" >::
ae 0 (count_rectangles [|" "|]);
"one rectangle" >::
ae 1 (count_rectangles [|"+-+";
"| |";
"+-+"|]);
"two rectangles without shared parts" >::
ae 2 (count_rectangles [|"  +-+";
"  | |";
"+-+-+";
"| |  ";
"+-+  "|]);
"five rectangles with shared parts" >::
ae 5 (count_rectangles [|"  +-+";
"  | |";
"+-+-+";
"| | |";
"+-+-+"|]);
"rectangle of height 1 is counted" >::
ae 1 (count_rectangles [|"+--+";
"+--+"|]);
"rectangle of width 1 is counted" >::
ae 1 (count_rectangles [|"++";
"||";
"++"|]);
"1x1 square is counted" >::
ae 1 (count_rectangles [|"++";
"++"|]);
"only complete rectangles are counted" >::
ae 1 (count_rectangles [|"  +-+";
"    |";
"+-+-+";
"| | -";
"+-+-+"|]);
"rectangles can be of different sizes" >::
ae 3 (count_rectangles [|"+------+----+";
"|      |    |";
"+---+--+    |";
"|   |       |";
"+---+-------+"|]);
"corner is required for a rectangle to be complete" >::
ae 2 (count_rectangles [|"+------+----+";
"|      |    |";
"+------+    |";
"|   |       |";
"+---+-------+"|]);
"large input with many rectangles" >::
ae 60 (count_rectangles [|"+---+--+----+";
"|   +--+----+";
"+---+--+    |";
"|   +--+----+";
"+---+--+--+-+";
"+---+--+--+-+";
"+------+  | |";
"          +-+"|]);
]

let () =
run_test_tt_main ("rectangles tests" >::: tests)``````
``````open Base

let is_vertice c = Char.(c = '+')

let is_h_edge c = Char.(c = '-' || is_vertice c)

let is_v_edge c = Char.(c = '|' || is_vertice c)

let is_rectangle diagram r c r' c' =
let range = Sequence.range
~start:`exclusive
~stop:`exclusive in
is_vertice diagram.(r).[c'] &&
is_vertice diagram.(r').[c] &&
(range c c'
|> Sequence.for_all
~f:(fun i ->
is_h_edge diagram.(r).[i] &&
is_h_edge diagram.(r').[i]
)
) &&
(range r r'
|> Sequence.for_all
~f:(fun i ->
is_v_edge diagram.(i).[c] &&
is_v_edge diagram.(i).[c']
)
)

let count_rectangles diagram =
let height = Array.length diagram in
let width = String.length diagram.(0) in
let count = ref 0 in
for r = 0 to height - 2 do
for c = 0 to width - 2 do
if is_vertice diagram.(r).[c]
then
for r' = r + 1 to height - 1 do
for c' = c + 1 to width - 1 do
if is_vertice diagram.(r').[c'] &&
is_rectangle diagram r c r' c'
then
Int.incr count
done
done
done
done;
!count

let count_rectangles diagram =
if Array.length diagram < 2 ||
String.length diagram.(0) < 2
then 0
else count_rectangles diagram``````