DHeap added (#118)

Author: prshnt19

pydatastructs/trees/__init__.py

@@ -22,6 +22,8 @@
 
 from .heaps import (
     BinaryHeap,
+    TernaryHeap,
+    DHeap,
     BinomialHeap
 )
 __all__.extend(heaps.__all__)

pydatastructs/trees/heaps.py

@@ -5,6 +5,8 @@
 
 __all__ = [
     'BinaryHeap',
+    'TernaryHeap',
+    'DHeap',
     'BinomialHeap'
 ]
 
@@ -14,9 +16,10 @@ class Heap(object):
     """
     pass
 
-class BinaryHeap(Heap):
+
+class DHeap(Heap):
     """
-    Represents Binary Heap.
+    Represents D-ary Heap.
 
     Parameters
     ==========
@@ -26,7 +29,6 @@ class BinaryHeap(Heap):
         List/tuple of initial elements in Heap.
 
     heap_property : str
-        The property of binary heap.
         If the key stored in each node is
         either greater than or equal to
         the keys in the node's children
@@ -41,8 +43,8 @@ class BinaryHeap(Heap):
     Examples
     ========
 
-    >>> from pydatastructs.trees.heaps import BinaryHeap
-    >>> min_heap = BinaryHeap(heap_property="min")
+    >>> from pydatastructs.trees.heaps import DHeap
+    >>> min_heap = DHeap(heap_property="min", d=3)
     >>> min_heap.insert(1, 1)
     >>> min_heap.insert(5, 5)
     >>> min_heap.insert(7, 7)
@@ -52,7 +54,7 @@ class BinaryHeap(Heap):
     >>> min_heap.extract().key
     4
 
-    >>> max_heap = BinaryHeap(heap_property='max')
+    >>> max_heap = DHeap(heap_property='max', d=2)
     >>> max_heap.insert(1, 1)
     >>> max_heap.insert(5, 5)
     >>> max_heap.insert(7, 7)
@@ -65,31 +67,32 @@ class BinaryHeap(Heap):
     References
     ==========
 
-    .. [1] https://en.m.wikipedia.org/wiki/Binary_heap
+    .. [1] https://en.wikipedia.org/wiki/D-ary_heap
     """
-    __slots__ = ['_comp', 'heap', 'heap_property', '_last_pos_filled']
+    __slots__ = ['_comp', 'heap', 'd', 'heap_property', '_last_pos_filled']
 
-    def __new__(cls, elements=None, heap_property="min"):
+    def __new__(cls, elements=None, heap_property="min", d=4):
         obj = Heap.__new__(cls)
         obj.heap_property = heap_property
+        obj.d = d
         if heap_property == "min":
             obj._comp = lambda key_parent, key_child: key_parent <= key_child
         elif heap_property == "max":
             obj._comp = lambda key_parent, key_child: key_parent >= key_child
         else:
             raise ValueError("%s is invalid heap property"%(heap_property))
         if elements is None:
-            elements = []
+            elements = DynamicOneDimensionalArray(TreeNode, 0)
         obj.heap = elements
-        obj._last_pos_filled = len(elements) - 1
+        obj._last_pos_filled = obj.heap._last_pos_filled
         obj._build()
         return obj
 
     def _build(self):
         for i in range(self._last_pos_filled + 1):
-            self.heap[i].left, self.heap[i].right = \
-                2*i + 1, 2*i + 2
-        for i in range((self._last_pos_filled + 1)//2, -1, -1):
+            self.heap[i]._leftmost, self.heap[i]._rightmost = \
+                self.d*i + 1, self.d*i + self.d
+        for i in range((self._last_pos_filled + 1)//self.d, -1, -1):
             self._heapify(i)
 
     def _swap(self, idx1, idx2):
@@ -103,23 +106,22 @@ def _swap(self, idx1, idx2):
     def _heapify(self, i):
         while True:
             target = i
-            l = 2*i + 1
-            r = 2*i + 2
+            l = self.d*i + 1
+            r = self.d*i + self.d
 
-            if l <= self._last_pos_filled:
-                target = l if self._comp(self.heap[l].key, self.heap[target].key) \
-                        else i
-            if r <= self._last_pos_filled:
-                target = r if self._comp(self.heap[r].key, self.heap[target].key) \
-                        else target
+            for j in range(l, r+1):
+                if j <= self._last_pos_filled:
+                    target = j if self._comp(self.heap[j].key, self.heap[target].key) \
+                            else target
+                else:
+                    break
 
             if target != i:
                 self._swap(target, i)
                 i = target
             else:
                 break
 
-
     def insert(self, key, data):
         """
         Insert a new element to the heap according to heap property.
@@ -141,10 +143,10 @@ def insert(self, key, data):
         self.heap.append(new_node)
         self._last_pos_filled += 1
         i = self._last_pos_filled
-        self.heap[i].left, self.heap[i].right = 2*i + 1, 2*i + 2
+        self.heap[i]._leftmost, self.heap[i]._rightmost = self.d*i + 1, self.d*i + self.d
 
         while True:
-            parent = (i - 1)//2
+            parent = (i - 1)//self.d
             if i == 0 or self._comp(self.heap[parent].key, self.heap[i].key):
                 break
             else:
@@ -169,23 +171,143 @@ def extract(self):
         else:
             element_to_be_extracted = TreeNode(self.heap[0].key, self.heap[0].data)
             self._swap(0, self._last_pos_filled)
-            self.heap[self._last_pos_filled] = TreeNode(float('inf') if self.heap_property == 'min'
-                                                                else float('-inf'), None)
-            self._heapify(0)
-            self.heap.pop()
+            self.heap.delete(self._last_pos_filled)
             self._last_pos_filled -= 1
+            self._heapify(0)
             return element_to_be_extracted
 
     def __str__(self):
         to_be_printed = ['' for i in range(self._last_pos_filled + 1)]
         for i in range(self._last_pos_filled + 1):
             node = self.heap[i]
-            to_be_printed[i] = (node.left if node.left <= self._last_pos_filled else None,
-                                node.key, node.data,
-                                node.right if node.right <= self._last_pos_filled else None)
+            if node._leftmost <= self._last_pos_filled:
+                if node._rightmost <= self._last_pos_filled:
+                    children = [x for x in range(node._leftmost, node._rightmost + 1)]
+                else:
+                    children = [x for x in range(node._leftmost, self._last_pos_filled + 1)]
+            else:
+                children = []
+            to_be_printed[i] = (node.key, node.data, children)
         return str(to_be_printed)
 
 
+class BinaryHeap(DHeap):
+    """
+    Represents Binary Heap.
+
+    Parameters
+    ==========
+
+    elements : list, tuple
+        Optional, by default 'None'.
+        List/tuple of initial elements in Heap.
+
+    heap_property : str
+        If the key stored in each node is
+        either greater than or equal to
+        the keys in the node's children
+        then pass 'max'.
+        If the key stored in each node is
+        either less than or equal to
+        the keys in the node's children
+        then pass 'min'.
+        By default, the heap property is
+        set to 'min'.
+
+    Examples
+    ========
+
+    >>> from pydatastructs.trees.heaps import BinaryHeap
+    >>> min_heap = BinaryHeap(heap_property="min")
+    >>> min_heap.insert(1, 1)
+    >>> min_heap.insert(5, 5)
+    >>> min_heap.insert(7, 7)
+    >>> min_heap.extract().key
+    1
+    >>> min_heap.insert(4, 4)
+    >>> min_heap.extract().key
+    4
+
+    >>> max_heap = BinaryHeap(heap_property='max')
+    >>> max_heap.insert(1, 1)
+    >>> max_heap.insert(5, 5)
+    >>> max_heap.insert(7, 7)
+    >>> max_heap.extract().key
+    7
+    >>> max_heap.insert(6, 6)
+    >>> max_heap.extract().key
+    6
+
+    References
+    ==========
+
+    .. [1] https://en.m.wikipedia.org/wiki/Binary_heap
+    """
+    def __new__(cls, elements=None, heap_property="min"):
+        obj = DHeap.__new__(cls, elements, heap_property, 2)
+        return obj
+
+
+class TernaryHeap(DHeap):
+    """
+    Represents Ternary Heap.
+
+    Parameters
+    ==========
+
+    elements : list, tuple
+        Optional, by default 'None'.
+        List/tuple of initial elements in Heap.
+
+    heap_property : str
+        If the key stored in each node is
+        either greater than or equal to
+        the keys in the node's children
+        then pass 'max'.
+        If the key stored in each node is
+        either less than or equal to
+        the keys in the node's children
+        then pass 'min'.
+        By default, the heap property is
+        set to 'min'.
+
+    Examples
+    ========
+
+    >>> from pydatastructs.trees.heaps import TernaryHeap
+    >>> min_heap = TernaryHeap(heap_property="min")
+    >>> min_heap.insert(1, 1)
+    >>> min_heap.insert(5, 5)
+    >>> min_heap.insert(7, 7)
+    >>> min_heap.insert(3, 3)
+    >>> min_heap.extract().key
+    1
+    >>> min_heap.insert(4, 4)
+    >>> min_heap.extract().key
+    3
+
+    >>> max_heap = TernaryHeap(heap_property='max')
+    >>> max_heap.insert(1, 1)
+    >>> max_heap.insert(5, 5)
+    >>> max_heap.insert(7, 7)
+    >>> min_heap.insert(3, 3)
+    >>> max_heap.extract().key
+    7
+    >>> max_heap.insert(6, 6)
+    >>> max_heap.extract().key
+    6
+
+    References
+    ==========
+
+    .. [1] https://en.wikipedia.org/wiki/D-ary_heap
+    .. [2] https://ece.uwaterloo.ca/~dwharder/aads/Algorithms/d-ary_heaps/Ternary_heaps/
+    """
+    def __new__(cls, elements=None, heap_property="min"):
+        obj = DHeap.__new__(cls, elements, heap_property, 3)
+        return obj
+
+
 class BinomialHeap(Heap):
     """
     Represents binomial heap.