add armstrong_numbers

concepts/enums/.meta/config.json

@@ -0,0 +1,7 @@
+{
+    "blurb": "<todo>",
+    "authors": [
+        "misicnenad"
+    ],
+    "contributors": []
+}

concepts/enums/about.md

@@ -0,0 +1 @@
+# Enums

concepts/enums/introduction.md

@@ -0,0 +1 @@
+# Introduction

concepts/enums/links.json

@@ -0,0 +1 @@
+[]

concepts/match-basics/.meta/config.json

@@ -0,0 +1,7 @@
+{
+    "blurb": "<todo>",
+    "authors": [
+        "misicnenad"
+    ],
+    "contributors": []
+}

concepts/match-basics/about.md

@@ -0,0 +1 @@
+# Match Basics

concepts/match-basics/introduction.md

@@ -0,0 +1 @@
+# Introduction

concepts/match-basics/links.json

@@ -0,0 +1 @@
+[]

config.json

@@ -62,6 +62,23 @@
         "topics": [
           "conditionals"
         ]
+      },
+      {
+        "slug": "armstrong-numbers",
+        "name": "Armstrong Numbers",
+        "uuid": "4aaa153d-3416-4101-8143-35b068a15451",
+        "practices": [
+          "functions",
+          "integers",
+          "enums"
+        ],
+        "prerequisites": [],
+        "difficulty": 1,
+        "topics": [
+          "math",
+          "option_type",
+          "result_type"
+        ]
       }
     ]
   },
@@ -76,10 +93,30 @@
       "slug": "integers",
       "name": "Integers"
     },
+    {
+      "uuid": "fe33b75a-8064-419d-9e09-16b49e6a5c6d",
+      "slug": "felts",
+      "name": "Felt Type"
+    },
     {
       "uuid": "de254443-42ee-4787-bc1e-3d0d2039c4f5",
       "slug": "booleans",
       "name": "Booleans"
+    },
+    {
+      "uuid": "6ba0e79b-9e70-4116-8f26-cce676a7b05e",
+      "slug": "functions",
+      "name": "Functions"
+    },
+    {
+      "uuid": "cff7568f-423e-4d6b-b238-1ebbce31d991",
+      "slug": "enums",
+      "name": "Enums"
+    },
+    {
+      "uuid": "2cc6431d-fc19-47f3-b7f1-999ed16e5244",
+      "slug": "match-basics",
+      "name": "Match Basics"
     }
   ],
   "key_features": [

exercises/practice/armstrong-numbers/.docs/instructions.md

@@ -0,0 +1,14 @@
+# Instructions
+
+An [Armstrong number][armstrong-number] is a number that is the sum of its own digits each raised to the power of the number of digits.
+
+For example:
+
+- 9 is an Armstrong number, because `9 = 9^1 = 9`
+- 10 is _not_ an Armstrong number, because `10 != 1^2 + 0^2 = 1`
+- 153 is an Armstrong number, because: `153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153`
+- 154 is _not_ an Armstrong number, because: `154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190`
+
+Write some code to determine whether a number is an Armstrong number.
+
+[armstrong-number]: https://en.wikipedia.org/wiki/Narcissistic_number

exercises/practice/armstrong-numbers/.meta/config.json

@@ -0,0 +1,20 @@
+{
+  "authors": [
+    "misicnenad"
+  ],
+  "files": {
+    "solution": [
+      "src/lib.cairo",
+      "Scarb.toml"
+    ],
+    "test": [
+      "src/tests.cairo"
+    ],
+    "example": [
+      ".meta/example.cairo"
+    ]
+  },
+  "blurb": "Determine if a number is an Armstrong number.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Narcissistic_number"
+}

exercises/practice/armstrong-numbers/.meta/example.cairo

@@ -0,0 +1,40 @@
+use core::integer::{u32_overflowing_add};
+
+fn is_armstrong_number(num: u32) -> bool {
+    let s = format!("{}", num);
+    let l = s.len();
+    let mut result: Option<u32> = Option::Some(0);
+    let mut i = l;
+    while i != 0 {
+        if let Option::None = result {
+            break;
+        }
+
+        i -= 1;
+
+        // ByteArray.at returns the ASCII representation of the character,
+        // so we need to subtract the position of the decimal '0' in ASCII
+        // (ASCII 48 == 0)
+        let digit: u8 = s.at(i).into().unwrap() - 48;
+
+        result = match u32_overflowing_add(result.unwrap(), pow(digit, l)) {
+            Result::Ok(val) => Option::Some(val),
+            Result::Err(_) => Option::None,
+        };
+    };
+
+    result == Option::Some(num)
+}
+
+fn pow(base: u8, exponent: u32) -> u32 {
+    let mut result: u32 = 1;
+    let mut i = exponent;
+    while i != 0 {
+        result *= base.into(); // cast u8 into u32
+        i -= 1;
+    };
+    result
+}
+
+#[cfg(test)]
+mod tests;

exercises/practice/armstrong-numbers/.meta/tests.toml

@@ -0,0 +1,43 @@
+# 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.
+
+[c1ed103c-258d-45b2-be73-d8c6d9580c7b]
+description = "Zero is an Armstrong number"
+
+[579e8f03-9659-4b85-a1a2-d64350f6b17a]
+description = "Single-digit numbers are Armstrong numbers"
+
+[2d6db9dc-5bf8-4976-a90b-b2c2b9feba60]
+description = "There are no two-digit Armstrong numbers"
+
+[509c087f-e327-4113-a7d2-26a4e9d18283]
+description = "Three-digit number that is an Armstrong number"
+
+[7154547d-c2ce-468d-b214-4cb953b870cf]
+description = "Three-digit number that is not an Armstrong number"
+
+[6bac5b7b-42e9-4ecb-a8b0-4832229aa103]
+description = "Four-digit number that is an Armstrong number"
+
+[eed4b331-af80-45b5-a80b-19c9ea444b2e]
+description = "Four-digit number that is not an Armstrong number"
+
+[f971ced7-8d68-4758-aea1-d4194900b864]
+description = "Seven-digit number that is an Armstrong number"
+
+[7ee45d52-5d35-4fbd-b6f1-5c8cd8a67f18]
+description = "Seven-digit number that is not an Armstrong number"
+
+[5ee2fdf8-334e-4a46-bb8d-e5c19c02c148]
+description = "Armstrong number containing seven zeroes"
+
+[12ffbf10-307a-434e-b4ad-c925680e1dd4]
+description = "The largest and last Armstrong number"

exercises/practice/armstrong-numbers/Scarb.toml

@@ -0,0 +1,4 @@
+[package]
+name = "armstrong_numbers"
+version = "0.1.0"
+edition = "2023_11"

exercises/practice/armstrong-numbers/src/lib.cairo

@@ -0,0 +1,6 @@
+fn is_armstrong_number(num: u32) -> bool {
+    panic!("true if {num} is an armstrong number")
+}
+
+#[cfg(test)]
+mod tests;

exercises/practice/armstrong-numbers/src/tests.cairo

@@ -0,0 +1,69 @@
+use armstrong_numbers::is_armstrong_number;
+
+#[test]
+fn zero_is_an_armstrong_number() {
+    assert!(is_armstrong_number(0))
+}
+
+#[test]
+fn single_digit_numbers_are_armstrong_numbers() {
+    assert!(is_armstrong_number(5))
+}
+
+#[test]
+fn there_are_no_2_digit_armstrong_numbers() {
+    assert!(!is_armstrong_number(10))
+}
+
+#[test]
+fn three_digit_armstrong_number() {
+    assert!(is_armstrong_number(153))
+}
+
+#[test]
+fn three_digit_non_armstrong_number() {
+    assert!(!is_armstrong_number(100))
+}
+
+#[test]
+fn four_digit_armstrong_number() {
+    assert!(is_armstrong_number(9474))
+}
+
+#[test]
+fn four_digit_non_armstrong_number() {
+    assert!(!is_armstrong_number(9475))
+}
+
+#[test]
+fn seven_digit_armstrong_number() {
+    assert!(is_armstrong_number(9_926_315))
+}
+
+#[test]
+fn seven_digit_non_armstrong_number() {
+    assert!(!is_armstrong_number(9_926_316))
+}
+
+#[test]
+fn nine_digit_armstrong_number() {
+    assert!(is_armstrong_number(912_985_153));
+}
+
+#[test]
+fn nine_digit_non_armstrong_number() {
+    assert!(!is_armstrong_number(999_999_999));
+}
+
+#[test]
+fn ten_digit_non_armstrong_number() {
+    assert!(!is_armstrong_number(3_999_999_999));
+}
+
+// The following number has an Armstrong sum equal to 2^32 plus itself,
+// and therefore will be detected as an Armstrong number if you are
+// incorrectly using wrapping arithmetic.
+#[test]
+fn properly_handles_overflow() {
+    assert!(!is_armstrong_number(4_106_098_957));
+}