110.cpp

/**
 * Definition for a binary tree node.
 * 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 dfs(TreeNode* node, bool& res) {
        if (!node) return 0;
        int left = 0;
        int right = 0;
        if (node->left) left = dfs(node->left, res);
        if (node->right) right = dfs(node->right, res);
        if (abs(left - right) > 1) res = false;
        return max(left, right) + 1;
    }
    bool isBalanced(TreeNode* root) {
        bool res = true;
        dfs(root, res);
        return res;
    }
};