LeetCode/222.cpp at main · vys1n/LeetCode · GitHub

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#include <bits/stdc++.h>
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 countNodes(TreeNode* root) {
        if (!root) return 0;
        if (root && root->left == nullptr) return 1;

        int lh = lH(root);
        int rh = rH(root);

        if (lh == rh) return (1 << lh) - 1;

        return 1 + countNodes(root->left) + countNodes(root->right);
    }

    int lH(TreeNode* node) {
        int ht = 0;
        while (node) {
            ht++;
            node = node->left;
        }
        return ht;
    }

    int rH(TreeNode* node) {
        int ht = 0;
        while (node) {
            ht++;
            node = node->right;
        }
        return ht;
    }
};