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0222_count_complete_tree_nodes.java
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63 lines (48 loc) · 1.61 KB
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/*
* https://leetcode-cn.com/problems/count-complete-tree-nodes/submissions/
给出一个完全二叉树，求出该树的节点个数。
说明：完全二叉树的定义如下：在完全二叉树中，除了最底层节点可能没填满外，其余每层节点数都达到最大值，并且最下面一层的节点都集中在该层最左边的若干位置。若最底层为第 h 层，则该层包含 1~ 2h 个节点。
示例:
输入:
1
/ \
2 3
/ \ /
4 5 6
输出: 6
------------------------------------------------------------------------------------------
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 MySolution {
public int countNodes(TreeNode root) {
if (root == null)
return 0;
return 1 + countNodes(root.left) + countNodes(root.right);
}
}
class Solution {
public int countNodes(TreeNode root) {
if (root == null) return 0;
if (root.left == null) return 1;
if (root.right == null) return 2;
return countNodes(root.left) + countNodes(root.right) + 1;
}
}