[Vssue]0222.完全二叉树的节点个数.md

[youngyangyang04]

https://www.programmercarl.com/0222.%E5%AE%8C%E5%85%A8%E4%BA%8C%E5%8F%89%E6%A0%91%E7%9A%84%E8%8A%82%E7%82%B9%E4%B8%AA%E6%95%B0.html

[Du1in9]

class Solution {
    public int countNodes(TreeNode root) {
        if (root == null) return 0;             
        // TreeNode left = root.left;       // 1. 完全二叉树
        // TreeNode right = root.right;
        // int depth1 = 1, depth2 = 1;
        // while (left != null) {
        //     depth1++;
        //     left = left.left;
        // }
        // while (right != null) {
        //     depth2++;
        //     right = right.right;
        // }
        // if (depth1 == depth2)
        //     return (1 << depth1) - 1;    // 2. 普通二叉树
        return 1 + countNodes(root.left) + countNodes(root.right);
    }
}

[wcvanvan]

想请问一下logN * logN的时间复杂度是怎么算出来的呢？我感觉时间上界是每个节点都计算一次是否完全二叉树，总共的时间复杂度是NlogN