110. Balanced Binary Tree*
https://leetcode.com/problems/balanced-binary-tree/
题目描述
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.
C++ 实现 1
要保证左右子树都是 balanced 并且左右子树的高度差不超过 1. 感觉这道题的代码写法和 572. Subtree of Another Tree* 一致.
/**
* 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 {
private:
int height(TreeNode *root) {
if (!root) return 0;
return std::max(height(root->left), height(root->right)) + 1;
}
public:
bool isBalanced(TreeNode* root) {
if (!root) return true;
return std::abs(height(root->left) - height(root->right)) <= 1
&& isBalanced(root->left) && isBalanced(root->right);
}
};