Given a complete binary tree, count the number of nodes.
Note:
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.
Example:
Input:
1
/ 2 3
/ \ /
4 5 6
Output: 6
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public int countNodes(TreeNode root) { int left = leftCount(root); int right = rightCount(root); if (left != right) { return 1 + countNodes(root.left) + countNodes(root.right); } else { return (1 << left) - 1; } } private int leftCount(TreeNode cur) { int res = 0; while (cur != null) { res += 1; cur = cur.left; } return res; } private int rightCount(TreeNode cur) { int res = 0; while (cur != null) { res += 1; cur = cur.right; } return res; } }
[LC] 222. Count Complete Tree Nodes
原文：https://www.cnblogs.com/xuanlu/p/12199917.html