【Leetcode笔记】222.完全二叉树的节点个数

ACM模式代码：
递归；后序遍历；时间复杂度 O(n)

#include <iostream>
#include <queue>
using namespace std;

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() : val(0), left(nullptr), right(nullptr) {}
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
    TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
};

class Solution {
public:
    int getAllNums(TreeNode* node) {
        if (node == NULL) return 0;
        int left = getAllNums(node->left);
        int right = getAllNums(node->right);
        int num = left + right + 1;

        return num;
    }
    int countNodes(TreeNode* root) {
        return getAllNums(root);
    }
};

int main() {
    TreeNode* root = new TreeNode(1);
    root->left = new TreeNode(2);
    root->right = new TreeNode(3);
    root->left->left = new TreeNode(4);
    root->left->right = new TreeNode(5);
    root->right->left = new TreeNode(6);

    Solution solution;
    int count = solution.countNodes(root);
    cout << "Number of nodes in the binary tree: " << count << endl;

    return 0;
}