Add binary-search exercise

concepts/arrays/.meta/config.json

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+{
+    "blurb": "<todo>",
+    "authors": [
+        "misicnenad"
+    ],
+    "contributors": []
+}

concepts/arrays/about.md

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+# Arrays

concepts/arrays/introduction.md

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+# Introduction

concepts/arrays/links.json

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+[]

config.json

@@ -129,12 +129,24 @@
         "name": "Roman Numerals",
         "uuid": "3fb4bd2f-bc5f-4a67-b9cc-49a786245876",
         "practices": [
-           "tuples",
-           "traits",
-           "type-casting"
+          "tuples",
+          "traits",
+          "type-casting"
         ],
         "prerequisites": [],
         "difficulty": 2
+      },
+      {
+        "slug": "binary-search",
+        "name": "Binary Search",
+        "uuid": "46be407d-13b8-4a7f-9a9a-4cef93485ba7",
+        "practices": [
+          "arrays",
+          "enums",
+          "control-flow"
+        ],
+        "prerequisites": [],
+        "difficulty": 4
       }
     ],
     "foregone": [
@@ -211,6 +223,11 @@
       "uuid": "b0ea24b3-3520-42c2-9177-0550247fa2bd",
       "slug": "type-casting",
       "name": "Type Casting"
+    },
+    {
+      "uuid": "6b6dafdb-7868-4089-855a-eb6735b5de5c",
+      "slug": "arrays",
+      "name": "Arrays"
     }
   ],
   "key_features": [

exercises/practice/binary-search/.docs/instructions.md

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+# Instructions
+
+Your task is to implement a binary search algorithm.
+
+A binary search algorithm finds an item in a list by repeatedly splitting it in half, only keeping the half which contains the item we're looking for.
+It allows us to quickly narrow down the possible locations of our item until we find it, or until we've eliminated all possible locations.
+
+~~~~exercism/caution
+Binary search only works when a list has been sorted.
+~~~~
+
+The algorithm looks like this:
+
+- Find the middle element of a _sorted_ list and compare it with the item we're looking for.
+- If the middle element is our item, then we're done!
+- If the middle element is greater than our item, we can eliminate that element and all the elements **after** it.
+- If the middle element is less than our item, we can eliminate that element and all the elements **before** it.
+- If every element of the list has been eliminated then the item is not in the list.
+- Otherwise, repeat the process on the part of the list that has not been eliminated.
+
+Here's an example:
+
+Let's say we're looking for the number 23 in the following sorted list: `[4, 8, 12, 16, 23, 28, 32]`.
+
+- We start by comparing 23 with the middle element, 16.
+- Since 23 is greater than 16, we can eliminate the left half of the list, leaving us with `[23, 28, 32]`.
+- We then compare 23 with the new middle element, 28.
+- Since 23 is less than 28, we can eliminate the right half of the list: `[23]`.
+- We've found our item.

exercises/practice/binary-search/.docs/introduction.md

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+# Introduction
+
+You have stumbled upon a group of mathematicians who are also singer-songwriters.
+They have written a song for each of their favorite numbers, and, as you can imagine, they have a lot of favorite numbers (like [0][zero] or [73][seventy-three] or [6174][kaprekars-constant]).
+
+You are curious to hear the song for your favorite number, but with so many songs to wade through, finding the right song could take a while.
+Fortunately, they have organized their songs in a playlist sorted by the title — which is simply the number that the song is about.
+
+You realize that you can use a binary search algorithm to quickly find a song given the title.
+
+[zero]: https://en.wikipedia.org/wiki/0
+[seventy-three]: https://en.wikipedia.org/wiki/73_(number)
+[kaprekars-constant]: https://en.wikipedia.org/wiki/6174_(number)

exercises/practice/binary-search/.meta/config.json

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+{
+  "authors": [],
+  "files": {
+    "solution": [
+      "src/lib.cairo",
+      "Scarb.toml"
+    ],
+    "test": [
+      "src/tests.cairo"
+    ],
+    "example": [
+      ".meta/example.cairo"
+    ]
+  },
+  "blurb": "Implement a binary search algorithm.",
+  "source": "Wikipedia",
+  "source_url": "https://en.wikipedia.org/wiki/Binary_search_algorithm"
+}

exercises/practice/binary-search/.meta/example.cairo

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+pub fn find<T, +Drop<T>, +Copy<T>, +PartialOrd<T>>(
+    search_array: @Array<T>, value: T
+) -> Option<usize> {
+    let mut base = 0_usize;
+    let mut slice: Span<T> = search_array.span();
+
+    loop {
+        let head = slice.slice(0, slice.len() / 2);
+        let mut tail = slice.slice(slice.len() / 2, slice.len() - head.len());
+        if let Option::Some(middle_element) = tail.pop_front() {
+            if *middle_element < value {
+                base += head.len() + 1;
+                slice = tail.slice(0, tail.len());
+            } else if *middle_element > value {
+                slice = head;
+            } else {
+                break Option::Some(base + head.len());
+            }
+        } else {
+            break Option::None;
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests;

exercises/practice/binary-search/.meta/tests.toml

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+# 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.
+
+[b55c24a9-a98d-4379-a08c-2adcf8ebeee8]
+description = "finds a value in an array with one element"
+
+[73469346-b0a0-4011-89bf-989e443d503d]
+description = "finds a value in the middle of an array"
+
+[327bc482-ab85-424e-a724-fb4658e66ddb]
+description = "finds a value at the beginning of an array"
+
+[f9f94b16-fe5e-472c-85ea-c513804c7d59]
+description = "finds a value at the end of an array"
+
+[f0068905-26e3-4342-856d-ad153cadb338]
+description = "finds a value in an array of odd length"
+
+[fc316b12-c8b3-4f5e-9e89-532b3389de8c]
+description = "finds a value in an array of even length"
+
+[da7db20a-354f-49f7-a6a1-650a54998aa6]
+description = "identifies that a value is not included in the array"
+
+[95d869ff-3daf-4c79-b622-6e805c675f97]
+description = "a value smaller than the array's smallest value is not found"
+
+[8b24ef45-6e51-4a94-9eac-c2bf38fdb0ba]
+description = "a value larger than the array's largest value is not found"
+
+[f439a0fa-cf42-4262-8ad1-64bf41ce566a]
+description = "nothing is found in an empty array"
+
+[2c353967-b56d-40b8-acff-ce43115eed64]
+description = "nothing is found when the left and right bounds cross"

exercises/practice/binary-search/Scarb.toml

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+[package]
+name = "binary_search"
+version = "0.1.0"
+edition = "2023_11"

exercises/practice/binary-search/src/lib.cairo

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+pub fn find(search_array: @Array<usize>, value: usize) -> Option<usize> {
+    panic!(
+        "Using the binary search algorithm, find the element '{value}' in the array '{search_array:?}' and return its index."
+    )
+}
+
+#[cfg(test)]
+mod tests;

exercises/practice/binary-search/src/tests.cairo

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+use binary_search::find;
+
+#[test]
+fn finds_a_value_in_an_array_with_one_element() {
+    let arr: Array<u32> = array![6];
+    assert_eq!(find(@arr, 6), Option::Some(0));
+}
+
+#[test]
+fn finds_first_value_in_an_array_with_two_element() {
+    let arr: Array<u32> = array![1, 2];
+    assert_eq!(find(@arr, 1), Option::Some(0));
+}
+
+#[test]
+fn finds_second_value_in_an_array_with_two_element() {
+    let arr: Array<u32> = array![1, 2];
+    assert_eq!(find(@arr, 2), Option::Some(1));
+}
+
+#[test]
+fn finds_a_value_in_the_middle_of_an_array() {
+    let arr: Array<u32> = array![1, 3, 4, 6, 8, 9, 11];
+    assert_eq!(find(@arr, 6), Option::Some(3));
+}
+
+#[test]
+fn finds_a_value_at_the_beginning_of_an_array() {
+    let arr: Array<u32> = array![1, 3, 4, 6, 8, 9, 11];
+    assert_eq!(find(@arr, 1), Option::Some(0));
+}
+
+#[test]
+fn finds_a_value_at_the_end_of_an_array() {
+    let arr: Array<u32> = array![1, 3, 4, 6, 8, 9, 11];
+    assert_eq!(find(@arr, 11), Option::Some(6));
+}
+
+#[test]
+fn finds_a_value_in_an_array_of_odd_length() {
+    let arr: Array<u32> = array![1, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 634];
+    assert_eq!(find(@arr, 144), Option::Some(9));
+}
+
+#[test]
+fn finds_a_value_in_an_array_of_even_length() {
+    let arr: Array<u32> = array![1, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377];
+    assert_eq!(find(@arr, 21), Option::Some(5));
+}
+
+const OPTION_NONE: Option<usize> = Option::None;
+
+#[test]
+fn identifies_that_a_value_is_not_included_in_the_array() {
+    let arr: Array<u32> = array![1, 3, 4, 6, 8, 9, 11];
+    assert_eq!(find(@arr, 7), OPTION_NONE);
+}
+
+#[test]
+fn a_value_smaller_than_the_arrays_smallest_value_is_not_found() {
+    let arr: Array<u32> = array![1, 3, 4, 6, 8, 9, 11];
+    assert_eq!(find(@arr, 0), OPTION_NONE);
+}
+
+#[test]
+fn a_value_larger_than_the_arrays_largest_value_is_not_found() {
+    let arr: Array<u32> = array![1, 3, 4, 6, 8, 9, 11];
+    assert_eq!(find(@arr, 13), OPTION_NONE);
+}
+
+#[test]
+fn nothing_is_found_in_an_empty_array() {
+    let arr: Array<u32> = array![];
+    assert_eq!(find(@arr, 1), OPTION_NONE);
+}
+
+#[test]
+fn nothing_is_found_when_the_left_and_right_bounds_cross() {
+    let arr: Array<u32> = array![1, 2];
+    assert_eq!(find(@arr, 0), OPTION_NONE);
+}