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 left and right subtrees of every node differ in height by no more than 1.
Example 1:
Given the following tree [3,9,20,null,null,15,7]
:
3 / \ 9 20 / \ 15 7
Return true.
Example 2:
Given the following tree [1,2,2,3,3,null,null,4,4]
:
1 / \ 2 2 / \ 3 3 / \ 4 4
Return false.
考察:求二叉树的深度,平衡二叉树定义;
/**
* 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 == NULL)
return true;
if (abs(getDepth(root->left) - getDepth(root->right)) > 1)
return false;
return isBalanced(root->left) & isBalanced(root->right);
}
int getDepth(TreeNode* root) {
if (root == NULL)
return 0;
return max(getDepth(root->left), getDepth(root->right)) + 1;
}
};