剑指 Offer 55 - II. 平衡二叉树

class Solution {
public:
	bool isBalanced(TreeNode* root) {
		if (root == NULL) 
            return true;//如果该子树为空，则一定是平衡的（因为没有左右子树）
		if (abs(getHeight(root->left) - getHeight(root->right)) > 1) 
            return false;
		return isBalanced(root->left)&& isBalanced(root->right);
	}

    
	int getHeight(TreeNode* root)
	{
		if (root == NULL) return 0;
		int leftHeight = getHeight(root->left);
		int rightHeight = getHeight(root->right);
		return leftHeight > rightHeight ? leftHeight + 1 : rightHeight + 1;
	}
};