Heapsort (#243)

Author: HarsheetKakar

pydatastructs/linear_data_structures/__init__.py

@@ -24,6 +24,7 @@
     merge_sort_parallel,
     brick_sort,
     brick_sort_parallel,
+    heapsort,
     matrix_multiply_parallel
 )
 __all__.extend(algorithms.__all__)

pydatastructs/linear_data_structures/algorithms.py

@@ -8,6 +8,7 @@
     'merge_sort_parallel',
     'brick_sort',
     'brick_sort_parallel',
+    'heapsort',
     'matrix_multiply_parallel'
 ]
 
@@ -235,6 +236,64 @@ def brick_sort_parallel(array, num_threads, **kwargs):
     if _check_type(array, DynamicArray):
         array._modify(force=True)
 
+def heapsort(array, **kwargs):
+    """
+    Implements Heapsort algorithm.
+
+    Parameters
+    ==========
+
+    array: Array
+        The array which is to be sorted.
+    start: int
+        The starting index of the portion
+        which is to be sorted.
+        Optional, by default 0
+    end: int
+        The ending index of the portion which
+        is to be sorted.
+        Optional, by default the index
+        of the last position filled.
+
+    Examples
+    ========
+
+    >>> from pydatastructs import OneDimensionalArray, heapsort
+    >>> arr = OneDimensionalArray(int,[3, 2, 1])
+    >>> heapsort(arr)
+    >>> [arr[0], arr[1], arr[2]]
+    [1, 2, 3]
+
+    References
+    ==========
+
+    .. [1] https://en.wikipedia.org/wiki/Heapsort
+
+    Note
+    ====
+
+    This function does not support custom comparators as is the case with
+    other sorting functions in this file.
+    """
+    from pydatastructs.trees.heaps import BinaryHeap
+
+    start = kwargs.get('start', 0)
+    end = kwargs.get('end', len(array) - 1)
+
+    h = BinaryHeap(heap_property="min")
+    for i in range(start, end+1):
+        if array[i] is not None:
+            h.insert(array[i])
+        array[i] = None
+
+    i = start
+    while not h.is_empty:
+        array[i] = h.extract().key
+        i += 1
+
+    if _check_type(array, DynamicArray):
+        array._modify(force=True)
+
 def _matrix_multiply_helper(m1, m2, row, col):
     s = 0
     for i in range(len(m1)):

pydatastructs/linear_data_structures/tests/test_algorithms.py

@@ -1,7 +1,7 @@
 from pydatastructs import (
     merge_sort_parallel, DynamicOneDimensionalArray,
     OneDimensionalArray, brick_sort, brick_sort_parallel,
-    matrix_multiply_parallel)
+    heapsort, matrix_multiply_parallel)
 from pydatastructs.utils.raises_util import raises
 import random
 
@@ -50,6 +50,9 @@ def test_brick_sort():
 def test_brick_sort_parallel():
     _test_common_sort(brick_sort_parallel, num_threads=3)
 
+def test_heapsort():
+    _test_common_sort(heapsort)
+
 def test_matrix_multiply_parallel():
     ODA = OneDimensionalArray