Shell sort added

Author: johannes67890

benches/sort_benchmark.rs

@@ -4,6 +4,7 @@ use sorting_algorithm::bubblesort;
 use sorting_algorithm::mergesort;
 use sorting_algorithm::quicksort;
 use sorting_algorithm::insertionsort;
+use sorting_algorithm::shellsort;
 
 fn sorting_benchmarks(c: &mut Criterion) {
     let mut group = c.benchmark_group("Sorting Algorithms");
@@ -44,6 +45,15 @@ fn sorting_benchmarks(c: &mut Criterion) {
                 BatchSize::SmallInput,
             )
         });
+        // Shell sort benchmark (Time complexity: O(nlogn))
+        group.bench_function(BenchmarkId::new("Shell Sort", i), |b| {
+            b.iter_batched_ref(
+                || -> Vec<usize> { (0..i).map(|_| rng.sample(&range)).collect() },
+                |v| shellsort (v),
+                BatchSize::SmallInput,
+            )
+        });
+
     }
     group.finish();
 }

src/lib.rs

@@ -2,11 +2,13 @@ mod bubble_sort;
 mod quick_sort;
 mod insertion_sort;
 mod merge_sort;
+mod shell_sort;
 
 pub use bubble_sort::bubblesort;
 pub use quick_sort::quicksort;
 pub use insertion_sort::insertionsort;
 pub use merge_sort::mergesort;
+pub use shell_sort::shellsort;
 
 use rand::Rng;
 use std::{ops::Range, ops::RangeBounds, ops::Bound};

src/shell_sort.rs

@@ -0,0 +1,37 @@
+/// Shell sort
+/// 
+/// # Ilustration
+/// ``` ignore
+/// arr = [ 8, 5, 9, 2, 7 ]
+/// 
+/// gap = 5 / 2 = 2
+/// 
+/// [ 8, 5, 9, 2, 7 ] -> [ 5, 8, 2, 7, 9 ]
+/// 
+/// gap = 2 / 2 = 1
+/// 
+/// [ 5, 8, 2, 7, 9 ] -> [ 2, 5, 7, 8, 9 ]
+/// ```
+/// 
+/// # Complexity
+/// 
+/// | Best | Average | Worst |
+/// |------|---------|-------|
+/// | O(n) | O(n^2)  | O(n^2)|
+/// 
+pub fn shellsort<T: Ord + Copy>(arr: &mut [T]) {
+    let len = arr.len();
+    let mut gap = len / 2;
+    while gap > 0 {
+        for i in gap..len {
+            let temp = arr[i];
+            let mut j = i;
+            while j >= gap && arr[j - gap] > temp {
+                arr[j] = arr[j - gap];
+                j -= gap;
+            }
+            arr[j] = temp;
+        }
+        gap /= 2;
+    }
+}