Collatz

config.json

@@ -117,6 +117,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 6
+      },
+      {
+        "slug": "collatz-conjecture",
+        "name": "Collatz Conjecture",
+        "uuid": "dc42f98e-d0fe-4c0f-ab4d-1954cf839ea8",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 2
       }
     ]
   },

exercises/practice/collatz-conjecture/.docs/instructions.md

@@ -0,0 +1,3 @@
+# Instructions
+
+Given a positive integer, return the number of steps it takes to reach 1 according to the rules of the Collatz Conjecture.

exercises/practice/collatz-conjecture/.docs/introduction.md

@@ -0,0 +1,28 @@
+# Introduction
+
+One evening, you stumbled upon an old notebook filled with cryptic scribbles, as though someone had been obsessively chasing an idea.
+On one page, a single question stood out: **Can every number find its way to 1?**
+It was tied to something called the **Collatz Conjecture**, a puzzle that has baffled thinkers for decades.
+
+The rules were deceptively simple.
+Pick any positive integer.
+
+- If it's even, divide it by 2.
+- If it's odd, multiply it by 3 and add 1.
+
+Then, repeat these steps with the result, continuing indefinitely.
+
+Curious, you picked number 12 to test and began the journey:
+
+12 ➜ 6 ➜ 3 ➜ 10 ➜ 5 ➜ 16 ➜ 8 ➜ 4 ➜ 2 ➜ 1
+
+Counting from the second number (6), it took 9 steps to reach 1, and each time the rules repeated, the number kept changing.
+At first, the sequence seemed unpredictable — jumping up, down, and all over.
+Yet, the conjecture claims that no matter the starting number, we'll always end at 1.
+
+It was fascinating, but also puzzling.
+Why does this always seem to work?
+Could there be a number where the process breaks down, looping forever or escaping into infinity?
+The notebook suggested solving this could reveal something profound — and with it, fame, [fortune][collatz-prize], and a place in history awaits whoever could unlock its secrets.
+
+[collatz-prize]: https://mathprize.net/posts/collatz-conjecture/

exercises/practice/collatz-conjecture/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "quintuple-mallard"
+  ],
+  "files": {
+    "solution": [
+      "collatz-conjecture.nu"
+    ],
+    "test": [
+      "tests.nu"
+    ],
+    "example": [
+      ".meta/example.nu"
+    ]
+  },
+  "blurb": "Calculate the number of steps to reach 1 using the Collatz conjecture.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Collatz_conjecture"
+}

exercises/practice/collatz-conjecture/.meta/example.nu

@@ -0,0 +1,17 @@
+export def steps [number] {
+    if $number <= 0 {
+        error make {msg: "Only positive integers are allowed"}
+    }
+    mut number = $number
+    mut steps = 0
+    while $number != 1 {
+        $steps += 1
+        if ($number mod 2) == 1 {
+            $number *= 3
+            $number += 1
+        } else {
+            $number /= 2
+        }
+    }
+    $steps
+}

exercises/practice/collatz-conjecture/.meta/tests.toml

@@ -0,0 +1,38 @@
+# 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.
+
+[540a3d51-e7a6-47a5-92a3-4ad1838f0bfd]
+description = "zero steps for one"
+
+[3d76a0a6-ea84-444a-821a-f7857c2c1859]
+description = "divide if even"
+
+[754dea81-123c-429e-b8bc-db20b05a87b9]
+description = "even and odd steps"
+
+[ecfd0210-6f85-44f6-8280-f65534892ff6]
+description = "large number of even and odd steps"
+
+[7d4750e6-def9-4b86-aec7-9f7eb44f95a3]
+description = "zero is an error"
+include = false
+
+[2187673d-77d6-4543-975e-66df6c50e2da]
+description = "zero is an error"
+reimplements = "7d4750e6-def9-4b86-aec7-9f7eb44f95a3"
+
+[c6c795bf-a288-45e9-86a1-841359ad426d]
+description = "negative value is an error"
+include = false
+
+[ec11f479-56bc-47fd-a434-bcd7a31a7a2e]
+description = "negative value is an error"
+reimplements = "c6c795bf-a288-45e9-86a1-841359ad426d"

exercises/practice/collatz-conjecture/collatz-conjecture.nu

@@ -0,0 +1,3 @@
+export def steps [number] {
+    error make {msg: "Please implement steps"}
+}

exercises/practice/collatz-conjecture/tests.nu

@@ -0,0 +1,18 @@
+use collatz-conjecture.nu steps
+use std/assert
+# zero steps for one
+assert equal (steps 1) 0
+# divide if even
+assert equal (steps 16) 4
+# even and odd steps
+assert equal (steps 12) 9
+# large number of even and odd steps
+assert equal (steps 1000000) 152
+# zero is an error
+assert equal (try { steps 0 } catch {|e|
+  $e.msg
+}) "Only positive integers are allowed"
+# negative value is an error
+assert equal (try { steps (-15) } catch {|e|
+  $e.msg
+})  "Only positive integers are allowed"

exercises/practice/resistor-color-duo/.meta/config.json

@@ -15,6 +15,5 @@
   },
   "blurb": "Convert color codes, as used on resistors, to a numeric value.",
   "source": "Maud de Vries, Erik Schierboom",
-  "source_url": "https://github.com/exercism/problem-specifications/issues/1464",
-  "difficulty": 2
+  "source_url": "https://github.com/exercism/problem-specifications/issues/1464"
 }

exercises/practice/resistor-color-trio/.meta/config.json

@@ -15,6 +15,5 @@
   },
   "blurb": "Convert color codes, as used on resistors, to a human-readable label.",
   "source": "Maud de Vries, Erik Schierboom",
-  "source_url": "https://github.com/exercism/problem-specifications/issues/1549",
-  "difficulty": 4
+  "source_url": "https://github.com/exercism/problem-specifications/issues/1549"
 }

exercises/practice/resistor-color/.meta/config.json

@@ -15,6 +15,5 @@
   },
   "blurb": "Convert a resistor band's color to its numeric representation.",
   "source": "Maud de Vries, Erik Schierboom",
-  "source_url": "https://github.com/exercism/problem-specifications/issues/1458",
-  "difficulty": 1
+  "source_url": "https://github.com/exercism/problem-specifications/issues/1458"
 }

exercises/practice/strain/.meta/config.json

@@ -15,6 +15,5 @@
   },
   "blurb": "Implement the `keep` and `discard` operation on collections.",
   "source": "Conversation with James Edward Gray II",
-  "source_url": "http://graysoftinc.com/",
-  "difficulty": 2
+  "source_url": "http://graysoftinc.com/"
 }