110. Balanced Binary Tree (Easy)
https://leetcode.com/problems/balanced-binary-tree/
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.
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.
Solutions
class Solution {
public boolean isBalanced(TreeNode root) {
int ans = inverseTreeHeight(root);
return ans >= 0 ? true : false;
}
private int inverseTreeHeight(TreeNode root) {
if (root == null) {
return 0;
}
int left = inverseTreeHeight(root.left);
int right = inverseTreeHeight(root.right);
if (left == -1 || right == -1) {
return -1;
}
if (Math.abs(left - right) > 1) {
return -1;
}
return Math.max(left, right) + 1;
}
}