sorts: Add selection sort

sorts/src/lib.rs

@@ -1,14 +1,13 @@
-pub fn add(left: usize, right: usize) -> usize {
-    left + right
-}
+// Copyright (c) 2023 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be
+// found in the LICENSE file.
 
-#[cfg(test)]
-mod tests {
-    use super::*;
+#![deny(
+    warnings,
+    clippy::all,
+    clippy::cargo,
+    clippy::nursery,
+    clippy::pedantic
+)]
 
-    #[test]
-    fn it_works() {
-        let result = add(2, 2);
-        assert_eq!(result, 4);
-    }
-}
+pub mod selection_sort;

sorts/src/selection_sort.rs

@@ -0,0 +1,52 @@
+// Copyright (c) 2023 Xu Shaohua <[email protected]>. All rights reserved.
+// Use of this source is governed by General Public License that can be
+// found in the LICENSE file.
+
+/// Selection sort works as follows:
+/// - Find the smallest element in the array, and exchange it with the first
+/// element in the array.
+/// - Find the second smallest element in the array, and exchange it with the
+/// element in the second position.
+/// - Continue in this way until the entire array is sorted.
+///
+/// It takes about as long to run selection sort for a file that is already
+/// in order, or for a file with all keys equal, as it does for a randomly
+/// ordered file.
+///
+/// It is the method of choice for sorting files with huge items and small keys.
+/// For such applications, the cost of moving the data dominates the cost of
+/// making comparisons, and no algorithms can sort a file with substantially less
+/// data movement than selection sort.
+pub fn selection_sort(list: &mut [i32]) {
+    if list.is_empty() {
+        return;
+    }
+    let len = list.len();
+    for i in 0..(len - 1) {
+        let mut min_index = i;
+        for j in (i + 1)..len {
+            if list[min_index] > list[j] {
+                min_index = j;
+            }
+            if i != min_index {
+                list.swap(i, min_index);
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::selection_sort;
+
+    #[test]
+    fn test_selection_sort() {
+        let mut list = [0, 5, 3, 2, 2];
+        selectioin_sort(&mut list);
+        assert_eq!(list, [0, 2, 2, 3, 5]);
+
+        let mut list = [-2, -5, -45];
+        selection_sort(&mut list);
+        assert_eq!(list, [-45, -5, -2]);
+    }
+}