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;
return 1+count(root);
}
public static int count(TreeNode root){
if(root.left==null && root.right==null){
return 0;
}
int left=0;
int right=0;
if(root.left!=null) left=count(root.left)+1;
if(root.right!=null) right=count(root.right)+1;
return left+right;
}
}