[WIP] Implement exercise binary-search-tree

config.json

@@ -888,9 +888,22 @@
       "uuid": "6b7f7b1f-c388-4f4c-b924-84535cc5e1a0",
       "slug": "hexadecimal",
       "deprecated": true
+    },
+    {
+      "uuid": "6f196341-0ffc-9780-a7ca-1f817508247161cbcd9",
+      "slug": "binary-search-tree",
+      "core": false,
+      "unlocked_by": null,
+      "difficulty": 4,
+      "topics":[
+        "recursion",
+        "classes",
+        "trees",
+        "searching",
+        "object_oriented_programming"
+      ]
     }
   ],
   "foregone": [
-
   ]
 }

exercises/binary-search-tree/README.md

@@ -0,0 +1,52 @@
+Insert and search for numbers in a binary tree.
+
+When we need to represent sorted data, an array does not make a good
+data structure.
+
+Say we have the array `[1, 3, 4, 5]`, and we add 2 to it so it becomes
+`[1, 3, 4, 5, 2]` now we must sort the entire array again! We can
+improve on this by realizing that we only need to make space for the new
+item `[1, nil, 3, 4, 5]`, and then adding the item in the space we
+added. But this still requires us to shift many elements down by one.
+
+Binary Search Trees, however, can operate on sorted data much more
+efficiently.
+
+A binary search tree consists of a series of connected nodes. Each node
+contains a piece of data (e.g. the number 3), a variable named `left`,
+and a variable named `right`. The `left` and `right` variables point at
+`nil`, or other nodes. Since these other nodes in turn have other nodes
+beneath them, we say that the left and right variables are pointing at
+subtrees. All data in the left subtree is less than or equal to the
+current node's data, and all data in the right subtree is greater than
+the current node's data.
+
+For example, if we had a node containing the data 4, and we added the
+data 2, our tree would look like this:
+
+      4
+     /
+    2
+
+If we then added 6, it would look like this:
+
+      4
+     / \
+    2   6
+
+If we then added 3, it would look like this
+
+       4
+     /   \
+    2     6
+     \
+      3
+
+And if we then added 1, 5, and 7, it would look like this
+
+          4
+        /   \
+       /     \
+      2       6
+     / \     / \
+    1   3   5   7

exercises/binary-search-tree/binary_search_tree.py

@@ -0,0 +1,8 @@
+class TreeNode(object):
+    def __init__(self, value):
+        pass
+
+
+class BinarySearchTree(object):
+    def __init__(self):
+        pass

exercises/binary-search-tree/binary_search_tree_test.py

@@ -0,0 +1,35 @@
+import unittest
+
+from binary_search_tree import BinarySearchTree
+
+
+class BinarySearchTreeTests(unittest.TestCase):
+    bst = BinarySearchTree()
+
+    def test_add_integer_number1(self):
+        self.assertTrue(self.bst.add(7))
+
+    def test_add_integer_number2(self):
+        self.assertTrue(self.bst.add(1))
+
+    def test_add_integer_number3(self):
+        self.assertTrue(self.bst.add(6))
+
+    def test_add_integer_number4(self):
+        self.assertTrue(self.bst.add(5))
+
+    def test_add_float_number(self):
+        self.assertTrue(self.bst.add(7.5))
+
+    def test_search_valid_number1(self):
+        self.assertEqual(self.bst.search(7).value, 7)
+
+    def test_search_valid_number2(self):
+        self.assertEqual(self.bst.search(7.5).value, 7.5)
+
+    def test_search_valid_number3(self):
+        self.assertEqual(self.bst.search(1).value, 1)
+
+
+if __name__ == '__main__':
+    unittest.main()

exercises/binary-search-tree/example.py

@@ -0,0 +1,69 @@
+class TreeNode(object):
+    def __init__(self, value):
+        self.value = value
+        self.left_node = None
+        self.right_node = None
+
+    def __str__(self):
+        return str(self.value)
+
+
+class BinarySearchTree(object):
+    def __init__(self):
+        self.root = None
+
+    def add(self, value):
+        if(self.root is None):
+            self.root = TreeNode(value)
+            inserted = True
+            return inserted
+        else:
+            inserted = False
+            cur_node = self.root
+
+            while not inserted:
+                if(value < cur_node.value):
+                    if(cur_node.left_node):
+                        cur_node = cur_node.left_node
+                    else:
+                        cur_node.left_node = TreeNode(value)
+                        inserted = True
+                        return inserted
+                elif(value > cur_node.value):
+                    if(cur_node.right_node):
+                        cur_node = cur_node.right_node
+                    else:
+                        cur_node.right_node = TreeNode(value)
+                        inserted = True
+                        return inserted
+
+    def search(self, searched_number):
+        cur_node = self.root
+        found = False
+        while not found:
+            if(cur_node is None):
+                raise ValueError("Element not found")
+            elif(searched_number < cur_node.value):
+                cur_node = cur_node.left_node
+            elif(searched_number > cur_node.value):
+                cur_node = cur_node.right_node
+            elif(searched_number == cur_node.value):
+                return cur_node
+
+    def print_inorder(self, node):
+        if(node is not None):
+            self.print_inorder(node.left_node)
+            print(node.value)
+            self.print_inorder(node.right_node)
+
+    def print_preorder(self, node):
+        if(node is not None):
+            print(node.value)
+            self.print_preorder(node.left_node)
+            self.print_preorder(node.right_node)
+
+    def print_postorder(self, node):
+        if(node is not None):
+            self.print_preorder(node.left_node)
+            self.print_preorder(node.right_node)
+            print(node.value)