Add flash sort algorithm implementation

sorts/flash_sort.py

@@ -0,0 +1,117 @@
+import math
+
+def flash_sort(array: list[int]) -> list[int]:
+    """
+    Perform Flashsort on the given array.
+
+    Flashsort is a distribution-based sorting algorithm. It divides the array
+    into buckets based on value ranges and sorts within each bucket.
+
+    Args:
+        array (list[int]): List of integers to sort.
+
+    Returns:
+        list[int]: The sorted array.
+
+    Example:
+    >>> flash_sort([15, 13, 24, 7, 18, 3, 22, 9])
+    [3, 7, 9, 13, 15, 18, 22, 24]
+    >>> flash_sort([5, 1, 4, 2, 3])
+    [1, 2, 3, 4, 5]
+    """
+    n = len(array)
+    if n == 0:
+        return array
+
+    # Step 1: Find minimum and maximum values
+    min_value = min(array)
+    max_value = max(array)
+
+    if min_value == max_value:
+        return array  # All values are the same
+
+    # Step 2: Divide array into m buckets
+    m = max(math.floor(0.45 * n), 1)
+
+    # Step 3: Count the number of elements in each bucket
+    def get_bucket_id(value: int) -> int:
+        """
+        Get the bucket index for the given value.
+
+        Args:
+            value (int): The value to assign a bucket to.
+
+        Returns:
+            int: The index of the bucket.
+        """
+        return (m * (value - min_value)) // (max_value - min_value + 1)
+
+    bucket_counts = [0] * m
+    for value in array:
+        bucket_counts[get_bucket_id(value)] += 1
+
+    # Step 4: Convert the count to prefix sum
+    for i in range(1, m):
+        bucket_counts[i] += bucket_counts[i - 1]
+
+    # Step 5: Rearrange the elements
+    def find_swap_index(bucket_id: int) -> int:
+        """
+        Find the first index of the element in the bucket.
+        """
+        for ind in range(bucket_counts[bucket_id - 1], bucket_counts[bucket_id]):
+            if get_bucket_id(array[ind]) != bucket_id:
+                break
+        return ind
+
+    def arrange_bucket(i1: int, i2: int, bucket_id: int) -> None:
+        """
+        Arrange elements into the specified bucket.
+        """
+        for i in range(i1, i2):
+            current_bucket_id = get_bucket_id(array[i])
+            while current_bucket_id != bucket_id:
+                swap_index = find_swap_index(current_bucket_id)
+                array[i], array[swap_index] = array[swap_index], array[i]
+                current_bucket_id = get_bucket_id(array[i])
+
+    for bucket_id in range(m - 1):
+        if bucket_id == 0:
+            arrange_bucket(0, bucket_counts[bucket_id], bucket_id)
+        else:
+            arrange_bucket(bucket_counts[bucket_id - 1], bucket_counts[bucket_id], bucket_id)
+
+    # Step 6: Sort each bucket using insertion sort
+    def insertion_sort(sub_array: list[int]) -> list[int]:
+        """
+        Sort the given array using insertion sort.
+
+        Args:
+            sub_array (list[int]): List of integers to sort.
+
+        Returns:
+            list[int]: Sorted array.
+        """
+        for i in range(1, len(sub_array)):
+            temp = sub_array[i]
+            j = i - 1
+            while j >= 0 and temp < sub_array[j]:
+                sub_array[j + 1] = sub_array[j]
+                j -= 1
+            sub_array[j + 1] = temp
+        return sub_array
+
+    for i in range(m):
+        if i == 0:
+            array[0:bucket_counts[i]] = insertion_sort(array[0:bucket_counts[i]])
+        else:
+            array[bucket_counts[i - 1]:bucket_counts[i]] = insertion_sort(
+                array[bucket_counts[i - 1]:bucket_counts[i]]
+            )
+
+    return array
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()