Description

Submission

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isBalanced(TreeNode* root) {
        bool balanced = true;
        dfs(root, balanced);
        return balanced;
    }
private:
    int dfs(TreeNode* root, bool& balanced) {
        if(!root) return 0;
        int l = dfs(root->left, balanced) + 1;
        int r = dfs(root->right, balanced) + 1;
        if(abs(r - l) > 1) {
            balanced = false;
            return 0;
        }
        return max(l, r);
    }
};