[New practice exercise] Rectangles

config.json

@@ -1472,6 +1472,14 @@
         ],
         "difficulty": 4
       },
+      {
+        "slug": "rectangles",
+        "name": "Rectangles",
+        "uuid": "6284512a-b40a-4e81-8d4f-712d729cc419",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 4
+      },
       {
         "slug": "killer-sudoku-helper",
         "name": "Killer Sudoku Helper",

exercises/practice/rectangles/.docs/instructions.md

@@ -0,0 +1,63 @@
+# Instructions
+
+Count the rectangles in an ASCII diagram like the one below.
+
+```text
+   +--+
+  ++  |
++-++--+
+|  |  |
++--+--+
+```
+
+The above diagram contains these 6 rectangles:
+
+```text
+
+
++-----+
+|     |
++-----+
+```
+
+```text
+   +--+
+   |  |
+   |  |
+   |  |
+   +--+
+```
+
+```text
+   +--+
+   |  |
+   +--+
+
+
+```
+
+```text
+
+
+   +--+
+   |  |
+   +--+
+```
+
+```text
+
+
++--+
+|  |
++--+
+```
+
+```text
+
+  ++
+  ++
+
+
+```
+
+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).

exercises/practice/rectangles/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [
+    "colinleach"
+  ],
+  "files": {
+    "solution": [
+      "rectangles.jl"
+    ],
+    "test": [
+      "runtests.jl"
+    ],
+    "example": [
+      ".meta/example.jl"
+    ]
+  },
+  "blurb": "Count the rectangles in an ASCII diagram."
+}

exercises/practice/rectangles/.meta/example.jl

@@ -0,0 +1,40 @@
+struct Pt
+    c::Integer  # column
+    r::Integer  # row
+end
+
+function rectangles(strings)
+    corners = Set{Pt}()
+    horiz = Set{Pt}()
+    vert = Set{Pt}()
+    for (y, line) in enumerate(strings)
+        for (x, char) in enumerate(line)
+            if char == '+'
+                push!(corners, Pt(x, y))
+                # corners are also valid for top & bottom
+                push!(horiz, Pt(x, y))
+                push!(vert, Pt(x, y))
+            elseif char == '-'
+                push!(horiz, Pt(x, y))
+            elseif char == '|'
+                push!(vert, Pt(x, y))
+            end
+        end
+    end
+
+    # get top-left and bottom-right corners
+    possibles = [(pt1, pt2) for pt1 in corners, pt2 in corners 
+                    if pt1.r < pt2.r && pt1.c < pt2.c
+                        # check bottom-left and top-right
+                        && Pt(pt1.c, pt2.r) ∈ corners 
+                        && Pt(pt2.c, pt1.r) ∈ corners]
+
+    sides(pt1, pt2) = all([Pt(pt1.c, row) ∈ vert for row in pt1.r:pt2.r]) &&
+                        all([Pt(pt2.c, row) ∈ vert for row in pt1.r:pt2.r])
+
+    top_bottom(pt1, pt2) = all([Pt(col, pt1.r) ∈ horiz for col in pt1.c:pt2.c]) &&
+                            all([Pt(col, pt2.r) ∈ horiz for col in pt1.c:pt2.c])
+
+    [(pt1, pt2) for (pt1, pt2) in possibles 
+                if sides(pt1, pt2) && top_bottom(pt1, pt2)] |> length
+end

exercises/practice/rectangles/.meta/template.j2

@@ -0,0 +1,15 @@
+{%- import "generator_macros.j2" as macros with context -%}
+{{ macros.canonical_ref() }}
+
+{{ macros.header()}}
+{%- macro test_case(case) %}
+    {%- set input = case["input"] %}
+    @testset "{{ case["description"]}}" begin
+        @test rectangles({{ case["input"]["strings"] | replace("'", '"') }}) == {{ case["expected"] }}
+    end
+{% endmacro %}
+
+    {% for case in cases -%}
+    {{ test_case(case) }}
+    {% endfor %}
+end

exercises/practice/rectangles/.meta/tests.toml

@@ -0,0 +1,52 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[485b7bab-4150-40aa-a8db-73013427d08c]
+description = "no rows"
+
+[076929ed-27e8-45dc-b14b-08279944dc49]
+description = "no columns"
+
+[0a8abbd1-a0a4-4180-aa4e-65c1b1a073fa]
+description = "no rectangles"
+
+[a4ba42e9-4e7f-4973-b7c7-4ce0760ac6cd]
+description = "one rectangle"
+
+[ced06550-83da-4d23-98b7-d24152e0db93]
+description = "two rectangles without shared parts"
+
+[5942d69a-a07c-41c8-8b93-2d13877c706a]
+description = "five rectangles with shared parts"
+
+[82d70be4-ab37-4bf2-a433-e33778d3bbf1]
+description = "rectangle of height 1 is counted"
+
+[57f1bc0e-2782-401e-ab12-7c01d8bfc2e0]
+description = "rectangle of width 1 is counted"
+
+[ef0bb65c-bd80-4561-9535-efc4067054f9]
+description = "1x1 square is counted"
+
+[e1e1d444-e926-4d30-9bf3-7d8ec9a9e330]
+description = "only complete rectangles are counted"
+
+[ca021a84-1281-4a56-9b9b-af14113933a4]
+description = "rectangles can be of different sizes"
+
+[51f689a7-ef3f-41ae-aa2f-5ea09ad897ff]
+description = "corner is required for a rectangle to be complete"
+
+[d78fe379-8c1b-4d3c-bdf7-29bfb6f6dc66]
+description = "large input with many rectangles"
+
+[6ef24e0f-d191-46da-b929-4faca24b4cd2]
+description = "rectangles must have four sides"

exercises/practice/rectangles/rectangles.jl

@@ -0,0 +1,3 @@
+function rectangles(strings)
+
+end

exercises/practice/rectangles/runtests.jl

@@ -0,0 +1,70 @@
+# These tests are auto-generated with test data from:
+# https://github.com/exercism/problem-specifications/tree/main/exercises/rectangles/canonical-data.json
+# File last updated on 2026-08-02
+
+using Test
+
+include("rectangles.jl")
+
+@testset verbose = true "tests" begin
+    @testset "no rows" begin
+        @test rectangles([]) == 0
+    end
+
+    @testset "no columns" begin
+        @test rectangles([""]) == 0
+    end
+
+    @testset "no rectangles" begin
+        @test rectangles([" "]) == 0
+    end
+
+    @testset "one rectangle" begin
+        @test rectangles(["+-+", "| |", "+-+"]) == 1
+    end
+
+    @testset "two rectangles without shared parts" begin
+        @test rectangles(["  +-+", "  | |", "+-+-+", "| |  ", "+-+  "]) == 2
+    end
+
+    @testset "five rectangles with shared parts" begin
+        @test rectangles(["  +-+", "  | |", "+-+-+", "| | |", "+-+-+"]) == 5
+    end
+
+    @testset "rectangle of height 1 is counted" begin
+        @test rectangles(["+--+", "+--+"]) == 1
+    end
+
+    @testset "rectangle of width 1 is counted" begin
+        @test rectangles(["++", "||", "++"]) == 1
+    end
+
+    @testset "1x1 square is counted" begin
+        @test rectangles(["++", "++"]) == 1
+    end
+
+    @testset "only complete rectangles are counted" begin
+        @test rectangles(["  +-+", "    |", "+-+-+", "| | -", "+-+-+"]) == 1
+    end
+
+    @testset "rectangles can be of different sizes" begin
+        @test rectangles(["+------+----+", "|      |    |", "+---+--+    |",
+                          "|   |       |", "+---+-------+"]) == 3
+    end
+
+    @testset "corner is required for a rectangle to be complete" begin
+        @test rectangles(["+------+----+", "|      |    |", "+------+    |",
+                          "|   |       |", "+---+-------+"]) == 2
+    end
+
+    @testset "large input with many rectangles" begin
+        @test rectangles(["+---+--+----+", "|   +--+----+", "+---+--+    |",
+                          "|   +--+----+", "+---+--+--+-+", "+---+--+--+-+",
+                          "+------+  | |", "          +-+"]) == 60
+    end
+
+    @testset "rectangles must have four sides" begin
+        @test rectangles(["+-+ +-+", "| | | |", "+-+-+-+", "  | |  ", "+-+-+-+", "| | | |",
+                          "+-+ +-+"]) == 5
+    end
+end