Merge pull request #14 from Pratham1807/master

abranhe · web-flow · commit da7917c24f56 · 2018-10-11T14:34:41.000-04:00
Added Tree Sort
diff --git a/allalgorithms/sorting/__init__.py b/allalgorithms/sorting/__init__.py
@@ -5,3 +5,4 @@
 from .pidgeonhole_sort import pidgeonhole_sort
 from .stooge_sort import stooge_sort
 from .cocktail_shaker_sort import cocktail_shaker_sort
+from .tree_sort import tree_sort
diff --git a/allalgorithms/sorting/tree_sort.py b/allalgorithms/sorting/tree_sort.py
@@ -0,0 +1,48 @@
+class BinaryTreeNode(object):
+    #initial values for value,left and right
+    def __init__(self, value):
+        self.value = value
+        self.left = None
+        self.right = None
+
+
+# inserting a new node in the binary tree
+def insert(tree, item):
+    # if no initial element in the tree
+    if tree == None:
+        tree = BinaryTreeNode(item)
+    else:
+        if (item < tree.value):
+            # if left branch of the tree is empty
+            if (tree.left == None):
+                tree.left = BinaryTreeNode(item)
+            else:
+                insert(tree.left, item)
+        else:
+            # if right branch of the tree is empty
+            if (tree.right == None):
+                tree.right = BinaryTreeNode(item)
+            else:
+                insert(tree.right, item)
+    return tree
+
+# funtion for the inorder traversal of the binary tree
+def in_order_traversal(tree,a):
+    if (tree.left != None):
+        in_order_traversal(tree.left,a)
+    a.append(tree.value)
+    if (tree.right != None):
+        in_order_traversal(tree.right,a)
+
+
+def tree_sort(x):
+    # root node
+    t = insert(None, x[0]);
+    # inserting all elements in the binary tree
+    for i in x[1:]:
+        insert(t,i)
+    # the results of the inorder traversal of a binary tree is a sorted
+    a = []
+    in_order_traversal(t,a)
+    return a
+
diff --git a/docs/sorting/tree-sort.md b/docs/sorting/tree-sort.md
@@ -0,0 +1,38 @@
+# Tree Sort
+
+A tree sort is a sort algorithm that builds a binary search tree from the elements to be sorted, and then traverses the tree (in-order) so that the elements come out in sorted order. It has two phases:
+1. Frist is creating a binary search tree using the given array elements.
+2. Second phase is traversing the given binary search tree in inorder, thus resulting in a sorted array.
+
+**Performance**
+
+The average number of comparisions for this method is O(nlogn). But in worst case, number of comparisions is reduced by O(n^2), a case which arrives when the tree is skewed.
+
+
+
+## Install
+
+```
+pip install allalgorithms
+```
+
+## Usage
+
+```py
+from allalgorithms.sorting import tree_sort
+
+arr = [77, 2, 10, -2, 1, 7]
+
+print(tree_sort(arr))
+# -> [-2, 1, 2, 7, 10, 77]
+```
+
+## API
+
+### tree_sort(array)
+
+> Returns a sorted array
+
+##### Params:
+
+- `array`: Unsorted Array
diff --git a/tests/test_sorting.py b/tests/test_sorting.py
@@ -7,7 +7,8 @@
     selection_sort,
     pigeonhole_sort,
     stooge_sort,
-    cocktail_shaker_sort
+    cocktail_shaker_sort,
+    tree_sort
 )
 
 
@@ -32,6 +33,9 @@ def test_stooge_sort(self):
 
     def test_cocktail_shaker_sort(self):
         self.assertEqual([-44, 1, 2, 3, 7, 19], cocktail_shaker_sort([7, 3, 2, 19, -44, 1]))
+    
+    def tree_sort(self):
+        self.assertEqual([-44, 1, 2, 3, 7, 19], tree_sort([7, 3, 2, 19, -44, 1]))
 
 
 if __name__ == "__main__":
