Add 4.11

Author: StBogdan

chapter_4/p4_11.py

@@ -0,0 +1,61 @@
+from utils.graphs import BiNode
+from utils.treeviz import viz_tree
+import random
+
+class SizedNode(BiNode):
+    def __init__(self, val: int):
+        super().__init__(val)
+        self.size = 1
+
+    def insert(self, x: int):
+        if x > self.val:
+            if self.right:
+                self.right.insert(x)
+            else:
+                self.right = SizedNode(x)
+        else:
+            if self.left:
+                self.left.insert(x)
+            else:
+                self.left = SizedNode(x)
+        self.size += 1
+
+
+class BinarySearchTree:
+
+    def __init__(self):
+        self.root = None
+
+    def add(self, x: int):
+        if not self.root:
+            self.root = SizedNode(x)
+        else:
+            self.root.insert(x)
+
+    def getRandomNuber(self) -> int:
+        target = random.randint(1, self.root.size)
+        print(f"Target is {target}")
+        return self._get_inorder_number(self.root, target)
+
+    def _get_inorder_number(self, node: SizedNode, target:int) -> int:
+        right_size = node.right.size if node.right else 0
+        # print(f"Node is {node.val}\tsize is {node.size},\tright is {right_size}")
+        node_traversal_poz = node.size - right_size
+        # print(f"At poz {node_traversal_poz},\ttarget is target {target}")
+        if node_traversal_poz == target:
+            return node.val
+        elif node_traversal_poz < target:
+            return self._get_inorder_number(node.right, target - node_traversal_poz)
+        else:
+            return self._get_inorder_number(node.left, target) 
+
+
+if __name__ == "__main__":
+    stream = [5, 1, 4, 14, 15, 9, 7, 13, 3]
+    rbst = BinarySearchTree()
+    for x in stream:
+        rbst.add(x)
+
+    viz_tree(rbst.root)
+    print(rbst.root.size)
+    print(f"Getting a random node: {rbst.getRandomNuber()}")