修复 0654.最大二叉树.md Python3解法

1. 修复语法错误
2. 优化可读性

problems/0654.最大二叉树.md

@@ -258,16 +258,30 @@ class Solution {
 ## Python 
 
 ```python
-//递归法
 class Solution:
+    """最大二叉树 递归法"""
+
     def constructMaximumBinaryTree(self, nums: List[int]) -> TreeNode:
-        if not nums: return None   //终止条件
-        root = TreeNode(max(nums))   //新建节点
-        p = nums.index(root.val)   //找到最大值位置
-        if p > 0: //保证有左子树
-            root.left = self.constructMaximumBinaryTree(nums[:p])   //递归
-        if p < len(nums): //保证有右子树
-            root.right = self.constructMaximumBinaryTree(nums[p+1:])  //递归
+        return self.traversal(nums, 0, len(nums))
+
+    def traversal(self, nums: List[int], begin: int, end: int) -> TreeNode:
+        # 列表长度为0时返回空节点
+        if begin == end:
+            return None
+
+        # 找到最大的值和其对应的下标
+        max_index = begin
+        for i in range(begin, end):
+            if nums[i] > nums[max_index]:
+                max_index = i
+
+        # 构建当前节点
+        root = TreeNode(nums[max_index])
+
+        # 递归构建左右子树
+        root.left = self.traversal(nums, begin, max_index)
+        root.right = self.traversal(nums, max_index + 1, end)
+
         return root
 ```