LeetCode Balanced Binary Tree

题目：

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.

/**
* Definition for binary tree
* 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 == NULL)
return true;
else if(isBalanced(root->left) && isBalanced(root->right) && maxDistance(root->left, root->right) <= 1)
return true;
else
return false;

}
private:
int maxDepth(TreeNode *root) {
if(root == NULL)
return 0;
else
return max(maxDepth(root->left),maxDepth(root->right))+1;
}
int maxDistance(TreeNode *p, TreeNode *q) {
return maxDepth(p) > maxDepth(q) ? (maxDepth(p)-maxDepth(q)) : (maxDepth(q)-maxDepth(p));
}
};