https://exercism.org/tracks/rust/exercises/binary-search

rust/binary-search/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+edition = "2021"
+name = "binary-search"
+version = "1.3.0"
+
+[dependencies]
+
+[features]
+generic = []

rust/binary-search/src/lib.rs

@@ -0,0 +1,22 @@
+pub fn find(array: &[i32], key: i32) -> Option<usize> {
+    if array.len() == 0 {
+        return None;
+    }
+    let mut l: usize = 0;
+    let mut r: usize = array.len() - 1;
+    while l <= r {
+        let m: usize = (l + r) / 2;
+        if array[m] == key {
+            return Some(m);
+        }
+        if array[m] < key {
+            l = m + 1;
+        } else {
+            if m == 0 {
+                return None
+            }
+            r = m - 1;
+        }
+    }
+    None
+}

rust/binary-search/tests/binary-search.rs

@@ -0,0 +1,100 @@
+// The &[] borrows are required for the base exercise,
+// where `find` is not generic. Once `find` is made generic,
+// the borrows become needless. Since we want the tests to work
+// without clippy warnings for both people who take on the
+// additional challenge and people who don't, we disable this lint.
+#![allow(clippy::needless_borrows_for_generic_args)]
+
+use binary_search::find;
+
+#[test]
+fn finds_a_value_in_an_array_with_one_element() {
+    assert_eq!(find(&[6], 6), Some(0));
+}
+
+#[test]
+fn finds_first_value_in_an_array_with_two_element() {
+    assert_eq!(find(&[1, 2], 1), Some(0));
+}
+
+#[test]
+fn finds_second_value_in_an_array_with_two_element() {
+    assert_eq!(find(&[1, 2], 2), Some(1));
+}
+
+#[test]
+fn finds_a_value_in_the_middle_of_an_array() {
+    assert_eq!(find(&[1, 3, 4, 6, 8, 9, 11], 6), Some(3));
+}
+
+#[test]
+fn finds_a_value_at_the_beginning_of_an_array() {
+    assert_eq!(find(&[1, 3, 4, 6, 8, 9, 11], 1), Some(0));
+}
+
+#[test]
+fn finds_a_value_at_the_end_of_an_array() {
+    assert_eq!(find(&[1, 3, 4, 6, 8, 9, 11], 11), Some(6));
+}
+
+#[test]
+fn finds_a_value_in_an_array_of_odd_length() {
+    assert_eq!(
+        find(&[1, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 634], 144),
+        Some(9)
+    );
+}
+
+#[test]
+fn finds_a_value_in_an_array_of_even_length() {
+    assert_eq!(
+        find(&[1, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377], 21),
+        Some(5)
+    );
+}
+
+#[test]
+fn identifies_that_a_value_is_not_included_in_the_array() {
+    assert_eq!(find(&[1, 3, 4, 6, 8, 9, 11], 7), None);
+}
+
+#[test]
+fn a_value_smaller_than_the_arrays_smallest_value_is_not_included() {
+    assert_eq!(find(&[1, 3, 4, 6, 8, 9, 11], 0), None);
+}
+
+#[test]
+fn a_value_larger_than_the_arrays_largest_value_is_not_included() {
+    assert_eq!(find(&[1, 3, 4, 6, 8, 9, 11], 13), None);
+}
+
+#[test]
+fn nothing_is_included_in_an_empty_array() {
+    assert_eq!(find(&[], 1), None);
+}
+
+#[test]
+fn nothing_is_found_when_the_left_and_right_bounds_cross() {
+    assert_eq!(find(&[1, 2], 0), None);
+}
+
+#[test]
+#[cfg(feature = "generic")]
+fn works_for_arrays() {
+    assert_eq!(find([6], 6), Some(0));
+}
+
+#[test]
+#[cfg(feature = "generic")]
+fn works_for_vec() {
+    let vector = vec![6];
+    assert_eq!(find(&vector, 6), Some(0));
+    assert_eq!(find(vector, 6), Some(0));
+}
+
+#[test]
+#[cfg(feature = "generic")]
+fn works_for_str_elements() {
+    assert_eq!(find(["a"], "a"), Some(0));
+    assert_eq!(find(["a", "b"], "b"), Some(1));
+}