diff --git a/rust/binary-search/Cargo.toml b/rust/binary-search/Cargo.toml new file mode 100644 index 0000000..6cfecd6 --- /dev/null +++ b/rust/binary-search/Cargo.toml @@ -0,0 +1,9 @@ +[package] +edition = "2021" +name = "binary-search" +version = "1.3.0" + +[dependencies] + +[features] +generic = [] diff --git a/rust/binary-search/src/lib.rs b/rust/binary-search/src/lib.rs new file mode 100644 index 0000000..428ce49 --- /dev/null +++ b/rust/binary-search/src/lib.rs @@ -0,0 +1,22 @@ +pub fn find(array: &[i32], key: i32) -> Option { + 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 +} diff --git a/rust/binary-search/tests/binary-search.rs b/rust/binary-search/tests/binary-search.rs new file mode 100644 index 0000000..3f419af --- /dev/null +++ b/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)); +}