Improve Linear Search (#826)

* ref: improve linear search

* tests: verify test data

---------

Co-authored-by: Piotr Idzik <[email protected]>

src/searching/linear_search.rs

@@ -1,6 +1,15 @@
-use std::cmp::PartialEq;
-
-pub fn linear_search<T: PartialEq>(item: &T, arr: &[T]) -> Option<usize> {
+/// Performs a linear search on the given array, returning the index of the first occurrence of the item.
+///
+/// # Arguments
+///
+/// * `item` - A reference to the item to search for in the array.
+/// * `arr` - A slice of items to search within.
+///
+/// # Returns
+///
+/// * `Some(usize)` - The index of the first occurrence of the item, if found.
+/// * `None` - If the item is not found in the array.
+pub fn linear_search<T: Ord>(item: &T, arr: &[T]) -> Option<usize> {
     for (i, data) in arr.iter().enumerate() {
         if item == data {
             return Some(i);
@@ -14,36 +23,54 @@ pub fn linear_search<T: PartialEq>(item: &T, arr: &[T]) -> Option<usize> {
 mod tests {
     use super::*;
 
-    #[test]
-    fn search_strings() {
-        let index = linear_search(&"a", &["a", "b", "c", "d", "google", "zoo"]);
-        assert_eq!(index, Some(0));
-    }
-
-    #[test]
-    fn search_ints() {
-        let index = linear_search(&4, &[1, 2, 3, 4]);
-        assert_eq!(index, Some(3));
-
-        let index = linear_search(&3, &[1, 2, 3, 4]);
-        assert_eq!(index, Some(2));
-
-        let index = linear_search(&2, &[1, 2, 3, 4]);
-        assert_eq!(index, Some(1));
-
-        let index = linear_search(&1, &[1, 2, 3, 4]);
-        assert_eq!(index, Some(0));
-    }
-
-    #[test]
-    fn not_found() {
-        let index = linear_search(&5, &[1, 2, 3, 4]);
-        assert_eq!(index, None);
+    macro_rules! test_cases {
+        ($($name:ident: $tc:expr,)*) => {
+            $(
+                #[test]
+                fn $name() {
+                    let (item, arr, expected) = $tc;
+                    if let Some(expected_index) = expected {
+                        assert_eq!(arr[expected_index], item);
+                    }
+                    assert_eq!(linear_search(&item, arr), expected);
+                }
+            )*
+        }
     }
 
-    #[test]
-    fn empty() {
-        let index = linear_search(&1, &[]);
-        assert_eq!(index, None);
+    test_cases! {
+        empty: ("a", &[] as &[&str], None),
+        one_item_found: ("a", &["a"], Some(0)),
+        one_item_not_found: ("b", &["a"], None),
+        search_strings_asc_start: ("a", &["a", "b", "c", "d", "google", "zoo"], Some(0)),
+        search_strings_asc_middle: ("google", &["a", "b", "c", "d", "google", "zoo"], Some(4)),
+        search_strings_asc_last: ("zoo", &["a", "b", "c", "d", "google", "zoo"], Some(5)),
+        search_strings_asc_not_found: ("x", &["a", "b", "c", "d", "google", "zoo"], None),
+        search_strings_desc_start: ("zoo", &["zoo", "google", "d", "c", "b", "a"], Some(0)),
+        search_strings_desc_middle: ("google", &["zoo", "google", "d", "c", "b", "a"], Some(1)),
+        search_strings_desc_last: ("a", &["zoo", "google", "d", "c", "b", "a"], Some(5)),
+        search_strings_desc_not_found: ("x", &["zoo", "google", "d", "c", "b", "a"], None),
+        search_ints_asc_start: (1, &[1, 2, 3, 4], Some(0)),
+        search_ints_asc_middle: (3, &[1, 2, 3, 4], Some(2)),
+        search_ints_asc_end: (4, &[1, 2, 3, 4], Some(3)),
+        search_ints_asc_not_found: (5, &[1, 2, 3, 4], None),
+        search_ints_desc_start: (4, &[4, 3, 2, 1], Some(0)),
+        search_ints_desc_middle: (3, &[4, 3, 2, 1], Some(1)),
+        search_ints_desc_end: (1, &[4, 3, 2, 1], Some(3)),
+        search_ints_desc_not_found: (5, &[4, 3, 2, 1], None),
+        with_gaps_0: (0, &[1, 3, 8, 11], None),
+        with_gaps_1: (1, &[1, 3, 8, 11], Some(0)),
+        with_gaps_2: (2, &[1, 3, 8, 11], None),
+        with_gaps_3: (3, &[1, 3, 8, 11], Some(1)),
+        with_gaps_4: (4, &[1, 3, 8, 10], None),
+        with_gaps_5: (5, &[1, 3, 8, 10], None),
+        with_gaps_6: (6, &[1, 3, 8, 10], None),
+        with_gaps_7: (7, &[1, 3, 8, 11], None),
+        with_gaps_8: (8, &[1, 3, 8, 11], Some(2)),
+        with_gaps_9: (9, &[1, 3, 8, 11], None),
+        with_gaps_10: (10, &[1, 3, 8, 11], None),
+        with_gaps_11: (11, &[1, 3, 8, 11], Some(3)),
+        with_gaps_12: (12, &[1, 3, 8, 11], None),
+        with_gaps_13: (13, &[1, 3, 8, 11], None),
     }
 }