Leetcode

# 222. Count Complete Tree Nodes

by hooni posted May 05, 2020
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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() {}
*     TreeNode(int val) { this.val = val; }
*     TreeNode(int val, TreeNode left, TreeNode right) {
*         this.val = val;
*         this.left = left;
*         this.right = right;
*     }
* }
*/
class Solution {
public int countNodes(TreeNode root) {
if(root == null){
return 0;
}

int nodes = 0;

queue.offer(root);
while(queue.size() > 0){
int size = queue.size();
for(int i=0; i<size; i++){
nodes++;
TreeNode node = queue.poll();
if(node.left != null){
}
if(node.right != null){
}
}
}

return nodes;
}
}```

```/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode() {}
*     TreeNode(int val) { this.val = val; }
*     TreeNode(int val, TreeNode left, TreeNode right) {
*         this.val = val;
*         this.left = left;
*         this.right = right;
*     }
* }
*/
class Solution {
public int countNodes(TreeNode root) {
if(root == null){
return 0;
}

return 1 + countNodes(root.left) + countNodes(root.right);
}
}```

[문제] https://leetcode.com/problems/count-complete-tree-nodes/

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