add binary_tree and avl_tree python code

codes/python/chapter_tree/binary_tree_dfs.py

@@ -1,10 +1,80 @@
-'''
+"""
 File: binary_tree_dfs.py
 Created Time: 2022-11-25
 Author: Krahets (krahets@163.com)
-'''
+"""
 
 import sys, os.path as osp
 sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
 from include import *
 
+
+result = []
+
+
+def preOrder(root):
+    """
+    前序遍历二叉树
+    """
+    if root is None:
+        return
+
+    # 访问优先级：根结点 -> 左子树 -> 右子树
+    result.append(root.val)
+    preOrder(root=root.left)
+    preOrder(root=root.right)
+
+
+def inOrder(root):
+    """
+    中序遍历二叉树
+    """
+    if root is None:
+        return
+
+    # 访问优先级：左子树 -> 根结点 -> 右子树
+    inOrder(root=root.left)
+    result.append(root.val)
+    inOrder(root=root.right)
+
+
+def postOrder(root):
+    """
+    后序遍历二叉树
+    """
+    if root is None:
+        return
+
+    # 访问优先级：左子树 -> 右子树 -> 根结点
+    postOrder(root=root.left)
+    postOrder(root=root.right)
+    result.append(root.val)
+
+
+""" Driver Code """
+if __name__ == "__main__":
+    # 初始化二叉树
+    # 这里借助了一个从数组直接生成二叉树的函数
+    root = list_to_tree(
+        arr=[1, 2, 3, 4, 5, 6, 7, None, None, None, None, None, None, None, None]
+    )
+    print("\n初始化二叉树\n")
+    print_tree(root)
+
+    # 前序遍历
+    result = []
+    preOrder(root)
+    print("\n前序遍历的结点打印序列 = ", result)
+    assert result == [1, 2, 4, 5, 3, 6, 7]
+
+    # 中序遍历
+    result = []
+    inOrder(root)
+    print("\n中序遍历的结点打印序列 = ", result)
+    assert result == [4, 2, 5, 1, 6, 3, 7]
+
+    # 后序遍历
+    result = []
+    postOrder(root)
+    print("\n后序遍历的结点打印序列 = ", result)
+    assert result == [4, 5, 2, 6, 7, 3, 1]