[LeetCode] Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

判断一棵树是否是高度平衡的二叉树，高度平衡的二叉树的定义是：二叉树的每个节点两个子树的深度差不超过1.

所以需要我们递归求出每个节点的左右子树的最大深度。然后比较判断。

/**
 * 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) {
        if (root == nullptr)
            return true;
        int left = depth(root->left);
        int right = depth(root->right);
        return abs(left - right) <= 1 && isBalanced(root->left) && isBalanced(root->right);
        
    }
    int depth(TreeNode* root) {
        if (root == nullptr)
            return 0;
        return max(depth(root->left), depth(root->right)) + 1;
    }
};
// 9 ms