(Medium) Leetcode 222.Count Complete Tree Nodes

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, was completely filled, and all nodes As far left as possible. It can has between 1 and 2h nodes inclusive at the last level H.

Solution One: Recursive timeout

The code is as follows:

/** * 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) {        if (root==null) return 0;        int num1=0,num2=0;        Num1=count (root.left);        Num2=count (root.right);        return 1+num1+num2;                }    int count (TreeNode root) {        if (root==null) return 0;        int num1=0,num2=0;        if (root.left==null && root.right==null)             return 1;        if (root.left!=null)            num1=count (root.left);        if (root.right!=null)            num2=count (root.right);         return 1+num1+num2;}    }

Operation Result:

Solution Two: Hierarchy traversal, queue, timeout

The code is as follows:

/** * 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) {        if (root==null) return 0;              Queue<treenode> q=new linkedlist<> ();        Q.offer (root);        int num=1;        TreeNode Tmp=null;        while (!q.isempty ()) {            tmp=q.poll ();            if (tmp.left!=null) {                q.offer (tmp.left);                num++;            }            if (tmp.right!=null) {                q.offer (tmp.right);                num++;            }        }         return num;    }    }

Solution three: To be continued

(Medium) Leetcode 222.Count Complete Tree Nodes