完全二叉树节点和(引入满二叉树概念, 区分求解)

Author: cls1991

ProblemsList.md

@@ -141,6 +141,7 @@
 * 144\. [Binary Tree Preorder Traversal](https://leetcode.com/problems/binary-tree-preorder-traversal/description)
 * 145\. [Binary Tree Postorder Traversal](https://leetcode.com/problems/binary-tree-postorder-traversal/description)
 * 173\. [Binary Search Tree Iterator](https://leetcode.com/problems/binary-search-tree-iterator/description)
+* 222\. [Count Complete Tree Nodes](https://leetcode.com/problems/count-complete-tree-nodes/description)
 * 226\. [Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree/description)
 * 235\. [Lowest Common Ancestor of a Binary Search Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/description)
 * 236\. [Lowest Common Ancestor of a Binary Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/description)
@@ -164,7 +165,6 @@
 * 153\. [Find Minimum in Rotated Sorted Array](https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/description)
 * 154\. [Find Minimum in Rotated Sorted Array II](https://leetcode.com/problems/find-minimum-in-rotated-sorted-array-ii/description)
 * 162\. [Find Peak Element](https://leetcode.com/problems/find-peak-element/description)
-* 222\. [Count Complete Tree Nodes](https://leetcode.com/problems/count-complete-tree-nodes/description)
 * 230\. [Kth Smallest Element in a BST](https://leetcode.com/problems/kth-smallest-element-in-a-bst/description)
 * 275\. [H-Index II](https://leetcode.com/problems/h-index-ii/description)
 * 278\. [First Bad Version](https://leetcode.com/problems/first-bad-version/description)

Tree/222_CountCompleteTreeNodes.py

@@ -0,0 +1,53 @@
+# coding: utf8
+
+
+"""
+    题目链接: https://leetcode.com/problems/count-complete-tree-nodes/description.
+    题目描述:
+
+    Given a complete binary tree, count the number of nodes.
+
+    Definition of a complete binary tree from Wikipedia:
+    In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last
+    level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.
+
+"""
+
+
+# Definition for a binary tree node.
+class TreeNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.left = None
+        self.right = None
+
+
+class Solution(object):
+    def countNodes(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        if not root:
+            return 0
+
+        # 满二叉树, 直接返回
+        # 不然, leetcode大数据样例通不过测试
+        lh = self.left_tree_height(root)
+        rh = self.right_tree_height(root)
+        if lh == rh:
+            return pow(2, lh) - 1
+
+        return 1 + self.countNodes(root.left) + self.countNodes(root.right)
+
+    def left_tree_height(self, root):
+        if not root:
+            return 0
+
+        return 1 + self.left_tree_height(root.left)
+
+    def right_tree_height(self, root):
+        if not root:
+            return 0
+
+        return 1 + self.right_tree_height(root.right)