Add typing annotations to Python codes. (#411)

codes/python/modules/binary_tree.py

@@ -5,36 +5,26 @@ Author: Krahets (krahets@163.com)
 """
 
 import collections
+from typing import List, Deque, Optional
 
 class TreeNode:
-    """Definition for a binary tree node
-    """    
-    def __init__(self, val=0, left=None, right=None):
-        self.val = val      # 结点值
-        self.height = 0     # 结点高度
-        self.left = left    # 左子结点引用
-        self.right = right  # 右子结点引用
+    """ Definition for a binary tree node """
+    def __init__(self, val: int = 0, left: Optional['TreeNode'] = None, right: Optional['TreeNode'] = None):
+        self.val: int = val                    # 结点值
+        self.height: int = 0                   # 结点高度
+        self.left: Optional[TreeNode] = left   # 左子结点引用
+        self.right: Optional[TreeNode] = right # 右子结点引用
 
-    def __str__(self):
-        val = self.val
-        left_node_val = self.left.val if self.left else None
-        right_node_val = self.right.val if self.right else None
-        return "<TreeNode: {}, leftTreeNode: {}, rightTreeNode: {}>".format(val, left_node_val, right_node_val)
-
-    __repr__ = __str__
-
-
-def list_to_tree(arr):
-    """Generate a binary tree with a list
-    """
+def list_to_tree(arr: List[int]) -> Optional[TreeNode]:
+    """ Generate a binary tree with a list """
     if not arr:
         return None
     
-    i = 0
+    i: int = 0
     root = TreeNode(arr[0])
-    queue = collections.deque([root])
+    queue: Deque[TreeNode] = collections.deque([root])
     while queue:
-        node = queue.popleft()
+        node: TreeNode = queue.popleft()
         i += 1
         if i >= len(arr): break
         if arr[i] != None:
@@ -48,15 +38,14 @@ def list_to_tree(arr):
             
     return root
 
-def tree_to_list(root):
-    """Serialize a tree into an array
-    """    
+def tree_to_list(root: Optional[TreeNode]) -> List[int]:
+    """ Serialize a tree into an array """    
     if not root: return []
-    queue = collections.deque()
+    queue: Deque[TreeNode] = collections.deque()
     queue.append(root)
-    res = []
+    res: List[int] = []
     while queue:
-        node = queue.popleft()
+        node: Optional[TreeNode] = queue.popleft()
         if node:
             res.append(node.val)
             queue.append(node.left)
@@ -64,13 +53,12 @@ def tree_to_list(root):
         else: res.append(None)
     return res
 
-def get_tree_node(root, val):
-    """Get a tree node with specific value in a binary tree
-    """    
+def get_tree_node(root: Optional[TreeNode], val: int) -> Optional[TreeNode]:
+    """ Get a tree node with specific value in a binary tree """    
     if not root:
         return
     if root.val == val:
         return root
-    left = get_tree_node(root.left, val)
-    right = get_tree_node(root.right, val)
+    left: Optional[TreeNode] = get_tree_node(root.left, val)
+    right: Optional[TreeNode] = get_tree_node(root.right, val)
     return left if left else right