总结

1. 书上给出一个简洁代码, 说是会重复遍历.

2. 框架相同, 可以写出下面的代码

class Solution {public:	bool ans;	int getHeight(TreeNode *root) {		if(!ans)			return 0;		if(root == NULL)			return 0;		int lt = 0, rt = 0;		if(root->left&&ans) {			lt = 1+getHeight(root->left);		}		if(root->right&&ans)			rt = 1 + getHeight(root->right);		if(abs(lt-rt)>1)			ans = false;		return max(lt, rt);	}		bool isBalanced(TreeNode *root) {        ans = true;		if(root == NULL)			return true;		getHeight(root);		return ans;    }};