[difference-of-squares] Add new exercise

config.json

@@ -250,6 +250,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 2
+      },
+      {
+        "slug": "difference-of-squares",
+        "name": "Difference of Squares",
+        "uuid": "1065256b-5263-443f-9f67-28d0fa2e9b93",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
       }
     ]
   },

exercises/practice/difference-of-squares/.docs/instructions.md

@@ -0,0 +1,14 @@
+# Instructions
+
+Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
+
+The square of the sum of the first ten natural numbers is
+(1 + 2 + ... + 10)² = 55² = 3025.
+
+The sum of the squares of the first ten natural numbers is
+1² + 2² + ... + 10² = 385.
+
+Hence the difference between the square of the sum of the first ten natural numbers and the sum of the squares of the first ten natural numbers is 3025 - 385 = 2640.
+
+You are not expected to discover an efficient solution to this yourself from first principles; research is allowed, indeed, encouraged.
+Finding the best algorithm for the problem is a key skill in software engineering.

exercises/practice/difference-of-squares/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "IsaacG"
+  ],
+  "files": {
+    "solution": [
+      "difference_of_squares.gd"
+    ],
+    "test": [
+      "difference_of_squares_test.gd"
+    ],
+    "example": [
+      ".meta/example.gd"
+    ]
+  },
+  "blurb": "Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.",
+  "source": "Problem 6 at Project Euler",
+  "source_url": "https://projecteuler.net/problem=6"
+}

exercises/practice/difference-of-squares/.meta/example.gd

@@ -0,0 +1,16 @@
+func sum_of_squares(num: int) -> int:
+	var result: int = 0
+	for i in range(num + 1):
+		result += i * i
+	return result
+
+
+func square_of_sum(num: int) -> int:
+	var result: int = 0
+	for i in range(num + 1):
+		result += i
+	return result * result
+
+
+func difference_of_squares(num: int) -> int:
+	return square_of_sum(num) - sum_of_squares(num)

exercises/practice/difference-of-squares/.meta/template.j2

@@ -0,0 +1,7 @@
+{% for case in cases %}
+func test_{{ case.func_name }}(solution_script):
+	var inputs = {{ case.given | togdscript }}
+	var expected = {{ case.expected | togdscript }}
+	return [solution_script.{{ case.property | camel_to_snake }}(inputs), expected]
+
+{% endfor %}

exercises/practice/difference-of-squares/.meta/tests.toml

@@ -0,0 +1,37 @@
+# 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.
+
+[e46c542b-31fc-4506-bcae-6b62b3268537]
+description = "Square the sum of the numbers up to the given number -> square of sum 1"
+
+[9b3f96cb-638d-41ee-99b7-b4f9c0622948]
+description = "Square the sum of the numbers up to the given number -> square of sum 5"
+
+[54ba043f-3c35-4d43-86ff-3a41625d5e86]
+description = "Square the sum of the numbers up to the given number -> square of sum 100"
+
+[01d84507-b03e-4238-9395-dd61d03074b5]
+description = "Sum the squares of the numbers up to the given number -> sum of squares 1"
+
+[c93900cd-8cc2-4ca4-917b-dd3027023499]
+description = "Sum the squares of the numbers up to the given number -> sum of squares 5"
+
+[94807386-73e4-4d9e-8dec-69eb135b19e4]
+description = "Sum the squares of the numbers up to the given number -> sum of squares 100"
+
+[44f72ae6-31a7-437f-858d-2c0837adabb6]
+description = "Subtract sum of squares from square of sums -> difference of squares 1"
+
+[005cb2bf-a0c8-46f3-ae25-924029f8b00b]
+description = "Subtract sum of squares from square of sums -> difference of squares 5"
+
+[b1bf19de-9a16-41c0-a62b-1f02ecc0b036]
+description = "Subtract sum of squares from square of sums -> difference of squares 100"

exercises/practice/difference-of-squares/difference_of_squares.gd

@@ -0,0 +1,10 @@
+func sum_of_squares(num: int) -> int:
+	pass
+
+
+func square_of_sum(num: int) -> int:
+	pass
+
+
+func difference_of_squares(num: int) -> int:
+	pass

exercises/practice/difference-of-squares/difference_of_squares_test.gd

@@ -0,0 +1,52 @@
+func test_square_of_sum_1(solution_script):
+	var inputs = 1
+	var expected = 1
+	return [solution_script.square_of_sum(inputs), expected]
+
+
+func test_square_of_sum_5(solution_script):
+	var inputs = 5
+	var expected = 225
+	return [solution_script.square_of_sum(inputs), expected]
+
+
+func test_square_of_sum_100(solution_script):
+	var inputs = 100
+	var expected = 25502500
+	return [solution_script.square_of_sum(inputs), expected]
+
+
+func test_sum_of_squares_1(solution_script):
+	var inputs = 1
+	var expected = 1
+	return [solution_script.sum_of_squares(inputs), expected]
+
+
+func test_sum_of_squares_5(solution_script):
+	var inputs = 5
+	var expected = 55
+	return [solution_script.sum_of_squares(inputs), expected]
+
+
+func test_sum_of_squares_100(solution_script):
+	var inputs = 100
+	var expected = 338350
+	return [solution_script.sum_of_squares(inputs), expected]
+
+
+func test_difference_of_squares_1(solution_script):
+	var inputs = 1
+	var expected = 0
+	return [solution_script.difference_of_squares(inputs), expected]
+
+
+func test_difference_of_squares_5(solution_script):
+	var inputs = 5
+	var expected = 170
+	return [solution_script.difference_of_squares(inputs), expected]
+
+
+func test_difference_of_squares_100(solution_script):
+	var inputs = 100
+	var expected = 25164150
+	return [solution_script.difference_of_squares(inputs), expected]