Traversal algorithms for Binary Tree.

sorts/bogosort.py

@@ -11,6 +11,7 @@
 from __future__ import print_function
 import random
 
+
 def bogosort(collection):
     """Pure implementation of the bogosort algorithm in Python
     :param collection: some mutable ordered collection with heterogeneous
@@ -28,13 +29,13 @@ def bogosort(collection):
     def isSorted(collection):
         if len(collection) < 2:
             return True
-        for i in range(len(collection)-1):
-            if collection[i] > collection[i+1]:
+        for i in range(len(collection) - 1):
+            if collection[i] > collection[i + 1]:
                 return False
         return True
 
     while not isSorted(collection):
-    	random.shuffle(collection)
+        random.shuffle(collection)
     return collection
 
 if __name__ == '__main__':

sorts/bubble_sort.py

@@ -9,6 +9,7 @@
 For manual testing run:
 python bubble_sort.py
 """
+
 from __future__ import print_function
 
 

sorts/heap_sort.py

@@ -12,6 +12,7 @@
 
 from __future__ import print_function
 
+
 def heapify(unsorted, index, heap_size):
     largest = index
     left_index = 2 * index + 1
@@ -26,6 +27,7 @@ def heapify(unsorted, index, heap_size):
         unsorted[largest], unsorted[index] = unsorted[index], unsorted[largest]
         heapify(unsorted, largest, heap_size)
 
+
 def heap_sort(unsorted):
     '''
     Pure implementation of the heap sort algorithm in Python
@@ -44,7 +46,7 @@ def heap_sort(unsorted):
     [-45, -5, -2]
     '''
     n = len(unsorted)
-    for i in range(n//2 - 1, -1, -1):
+    for i in range(n // 2 - 1, -1, -1):
         heapify(unsorted, i, n)
     for i in range(n - 1, 0, -1):
         unsorted[0], unsorted[i] = unsorted[i], unsorted[0]

sorts/insertion_sort.py

@@ -30,8 +30,9 @@ def insertion_sort(collection):
     [-45, -5, -2]
     """
     for index in range(1, len(collection)):
-        while 0 < index and collection[index] < collection[index-1]:
-            collection[index], collection[index-1] = collection[index-1], collection[index]
+        while 0 < index and collection[index] < collection[index - 1]:
+            collection[index], collection[
+                index - 1] = collection[index - 1], collection[index]
             index -= 1
 
     return collection

sorts/selection_sort.py

@@ -17,7 +17,7 @@ def selection_sort(collection):
     :param collection: some mutable ordered collection with heterogeneous
     comparable items inside
     :return: the same collection ordered by ascending
-    
+
 
     Examples:
     >>> selection_sort([0, 5, 3, 2, 2])
@@ -29,7 +29,7 @@ def selection_sort(collection):
     >>> selection_sort([-2, -5, -45])
     [-45, -5, -2]
     """
-   
+
     length = len(collection)
     for i in range(length):
         least = i

sorts/shell_sort.py

@@ -17,31 +17,30 @@ def shell_sort(collection):
     :param collection:  Some mutable ordered collection with heterogeneous
     comparable items inside
     :return:  the same collection ordered by ascending
-    
+
     >>> shell_sort([0, 5, 3, 2, 2])
     [0, 2, 2, 3, 5]
 
     >>> shell_sort([])
     []
-     
-    >>> shell_sort([-2, -5, -45]) 
+
+    >>> shell_sort([-2, -5, -45])
     [-45, -5, -2]
     """
     # Marcin Ciura's gap sequence
     gaps = [701, 301, 132, 57, 23, 10, 4, 1]
-    
+
     for gap in gaps:
         i = gap
         while i < len(collection):
             temp = collection[i]
             j = i
-            while j >= gap and collection[j-gap] > temp:
+            while j >= gap and collection[j - gap] > temp:
                 collection[j] = collection[j - gap]
                 j -= gap
             collection[j] = temp
             i += 1
-
-
+
     return collection
 
 if __name__ == '__main__':

traverals/binary_tree_traversals.py

@@ -0,0 +1,105 @@
+"""
+This is pure python implementation of tree traversal algorithms
+"""
+
+import queue
+
+
+class TreeNode:
+
+    def __init__(self, data):
+        self.data = data
+        self.right = None
+        self.left = None
+
+
+def build_tree():
+    print("Enter the value of the root node: ", end="")
+    data = eval(input())
+    if data < 0:
+        return None
+    else:
+        q = queue.Queue()
+        tree_node = TreeNode(data)
+        q.put(tree_node)
+        while not q.empty():
+            node_found = q.get()
+            print("Enter the left node of %s: " % node_found.data, end="")
+            left_data = eval(input())
+            if left_data >= 0:
+                left_node = TreeNode(left_data)
+                node_found.left = left_node
+                q.put(left_node)
+            print("Enter the right node of %s: " % node_found.data, end="")
+            right_data = eval(input())
+            if right_data >= 0:
+                right_node = TreeNode(right_data)
+                node_found.right = right_node
+                q.put(right_node)
+    return tree_node
+
+
+def pre_order(node):
+    if not node:
+        return
+    print(node.data, end=" ")
+    pre_order(node.left)
+    pre_order(node.right)
+
+
+def in_order(node):
+    if not node:
+        return
+    pre_order(node.left)
+    print(node.data, end=" ")
+    pre_order(node.right)
+
+
+def post_order(node):
+    if not node:
+        return
+    post_order(node.left)
+    post_order(node.right)
+    print(node.data, end=" ")
+
+
+def level_order(node):
+    if not node:
+        return
+    q = queue.Queue()
+    q.put(node)
+    while not q.empty():
+        node_dequeued = q.get()
+        print(node_dequeued.data, end=" ")
+        if node_dequeued.left:
+            q.put(node_dequeued.left)
+        if node_dequeued.right:
+            q.put(node_dequeued.right)
+
+
+if __name__ == '__main__':
+    import sys
+    print("\n********* Binary Tree Traversals ************\n")
+    # For python 2.x and 3.x compatibility: 3.x has not raw_input builtin
+    # otherwise 2.x's input builtin function is too "smart"
+    if sys.version_info.major < 3:
+        input_function = raw_input
+    else:
+        input_function = input
+
+    node = build_tree()
+    print("\n********* Pre Order Traversal ************")
+    pre_order(node)
+    print("\n******************************************\n")
+
+    print("\n********* In Order Traversal ************")
+    in_order(node)
+    print("\n******************************************\n")
+
+    print("\n********* Post Order Traversal ************")
+    post_order(node)
+    print("\n******************************************\n")
+
+    print("\n********* Level Order Traversal ************")
+    level_order(node)
+    print("\n******************************************\n")