leetcode-110-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.

给定一棵二叉树，判断它是否平衡。一个平衡的二叉树的左右子树的深度差小于或等于1.

很简单的DFS问题，先判断左右子树是否为平衡二叉树，再判断它们的高度差是否在1以内。

/**
 * 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) return true;
        if(isBalanced(root->left)&&isBalanced(root->right))
            if(abs(height(root->left)-height(root->right))<2)
                return true;
        return false;

    }
    int height(TreeNode* root)
    {
        if(!root) return 0;
        return 1+max(height(root->left),height(root->right));
    }
};