Balanced Binary Tree
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 depth of the two subtrees of every node never differ by more than 1.
分析
无
代码
// Balanced Binary Tree
// 时间复杂度O(n),空间复杂度O(logn)
class Solution {
public:
bool isBalanced (TreeNode* root) {
return balancedHeight (root) >= 0;
}
/**
* Returns the height of `root` if `root` is a balanced tree,
* otherwise, returns `-1`.
*/
int balancedHeight (TreeNode* root) {
if (root == nullptr) return 0; // 终止条件
int left = balancedHeight (root->left);
int right = balancedHeight (root->right);
if (left < 0 || right < 0 || abs(left - right) > 1) return -1; // 剪枝
return max(left, right) + 1; // 三方合并
}
};