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;
}
Queue<TreeNode> queue = new LinkedList<>();
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){
queue.add(node.left);
}
if(node.right != null){
queue.add(node.right);
}
}
}
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/
