Count Complete Tree Nodes

时间:2023-03-08 16:06:19

Given a complete binary tree, count the number of nodes.

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.

 /**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int countNodes(TreeNode root) { int leftDepth = leftDepth(root);
int rightDepth = rightDepth(root); if (leftDepth == rightDepth) {
return ( << leftDepth) - ;
}
return + countNodes(root.left) + countNodes(root.right); } private int rightDepth(TreeNode root) {
int depth = ;
while (root != null) {
root = root.right;
depth++;
}
return depth;
} private int leftDepth(TreeNode root) {
int depth = ;
while (root != null) {
root = root.left;
depth++;
}
return depth;
}
}