Package g0201_0300.s0222_count_complete_tree_nodes

Class Solution

java.lang.Object
g0201_0300.s0222_count_complete_tree_nodes.Solution
public class Solution extends java.lang.Object
222 - Count Complete Tree Nodes.

Medium

Given the root of a complete binary tree, return the number of the nodes in the tree.

According to Wikipedia , every level, except possibly the last, is completely filled in a complete binary tree, 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.

Design an algorithm that runs in less than O(n) time complexity.

Example 1:

Input: root = [1,2,3,4,5,6]

Output: 6

Example 2:

Input: root = []

Output: 0

Example 3:

Input: root = [1]

Output: 1

Constraints:

  • The number of nodes in the tree is in the range [0, 5 * 104].
  • 0 <= Node.val <= 5 * 104
  • The tree is guaranteed to be complete.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    countNodes(TreeNode root)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • countNodes

      public int countNodes(TreeNode root)