LeetCode 222. 完全二叉树的节点个数 中等

我的解题

递归

我是按照 labuladong 东哥手把手带你套框架刷通二叉树|第一期 中给出的算法写的:

#include <bits/stdc++.h>
using namespace std;

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

struct TreeNode
{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) :
                    val(x), left(NULL), right(NULL)
    {
    }
};
class Solution
{
public:
    int countNodes(TreeNode *root)
    {
        if (root == nullptr)
        {
            return 0;
        }
        return 1 + countNodes(root->left) + countNodes(root->right);
    }
};

int main()
{
    TreeNode n1 { 1 };
    TreeNode n2 { 2 };
    TreeNode n3 { 3 };
    TreeNode n4 { 4 };
    TreeNode n5 { 5 };
    TreeNode n6 { 6 };
    n1.left = &n2;
    n1.right = &n5;
    n2.left = &n3;
    n2.right = &n4;
    n5.right = &n6;
    Solution s;
    s.countNodes(&n1);
}