Satellite

practice/satellite/satellite.py

@@ -1,2 +1,103 @@
+class Node:
+    """
+    A class to represent a node in a binary tree.
+
+    Attributes
+    ----------
+    value : int
+        The value of the node.
+    left : Node, optional
+        The left child of the node (default is None).
+    right : Node, optional
+        The right child of the node (default is None).
+
+    Methods
+    -------
+    to_dict():
+        Converts the node and its children into a dictionary.
+    """
+
+    def __init__(self, value, left=None, right=None):
+        """
+        Constructs all the necessary attributes for the Node object.
+
+        Parameters
+        ----------
+            value : int
+                The value of the node.
+            left : Node, optional
+                The left child of the node (default is None).
+            right : Node, optional
+                The right child of the node (default is None).
+        """
+        self.value = value
+        self.left = left
+        self.right = right
+
+    def to_dict(self):
+        """
+        Converts the node and its children into a dictionary.
+
+        Returns
+        -------
+        dict
+            A dictionary with keys 'v', 'l', 'r' representing value, left child, and right child respectively.
+        """
+        return {
+            "v": self.value,
+            "l": self.left.to_dict() if self.left else {},
+            "r": self.right.to_dict() if self.right else {},
+        }
+
+
 def tree_from_traversals(preorder, inorder):
-    pass
+    """
+    Constructs a binary tree from its preorder and inorder traversals.
+
+    Parameters
+    ----------
+    preorder : list
+        The preorder traversal of the tree.
+    inorder : list
+        The inorder traversal of the tree.
+
+    Returns
+    -------
+    dict
+        A dictionary representing the tree.
+
+    Raises
+    ------
+    ValueError
+        If the lengths of preorder and inorder are not the same,
+        or if they do not contain the same elements,
+        or if they do not contain unique items.
+    """
+    if len(preorder) != len(inorder):
+        raise ValueError("traversals must have the same length")
+
+    if sorted(preorder) != sorted(inorder):
+        raise ValueError("traversals must have the same elements")
+
+    if len(set(preorder)) != len(preorder):
+        raise ValueError("traversals must contain unique items")
+
+    if not preorder and not inorder:
+        return {}
+
+    root_value = preorder[0]
+    root_index = inorder.index(root_value)
+
+    left_subtree = tree_from_traversals(preorder[1:root_index+1], inorder[:root_index])
+    right_subtree = tree_from_traversals(preorder[root_index+1:], inorder[root_index+1:])
+
+    if isinstance(left_subtree, Node):
+        left_subtree = left_subtree.to_dict()
+    if isinstance(right_subtree, Node):
+        right_subtree = right_subtree.to_dict()
+
+    return {
+        "v": root_value,
+        "l": left_subtree,
+        "r": right_subtree,
+    }