LeetCode：110_Balanced Binary Tree | 平衡二叉树 | Easy

要求：判断一棵树是否是平衡二叉树

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 .
 

代码如下：

 struct TreeNode {
     int            val;
     TreeNode    *left;
     TreeNode    *right;
     TreeNode(int x): val(x),left(NULL), right(NULL) {}
 };

 int maxTreeDepth(TreeNode *root) //先求树的深度
 {
     if (NULL == root)
         return ;
     int lval = maxTreeDepth(root->left);
     int rval = maxTreeDepth(root->right);
     return  + (lval > rval ? lval:rval);
 }
 bool isBalanced(TreeNode *root)//根据树的深度再来判断是否是平衡树
 {
     if(NULL == root)
         return true;
     int diff = maxTreeDepth(root->left) - maxTreeDepth(root->right);
     if (diff < - || diff > )
         return false;
     return isBalanced(root->left) && isBalanced(root->right);
 }