110. 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.

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(E) Maximum Depth of Binary Tree

/**
* Definition for binary tree
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public boolean isBalanced(TreeNode root) {
if (depth(root) == -1)
return false;
return true;
}

private int depth(TreeNode root) {
if (root == null)
return 0;
int left = depth(root.left);
int right = depth(root.right);
// If any subtree fails, all parent nodes should fail. No need to calculate depth.
if (left == -1 || right == -1 || Math.abs(left-right) > 1)
return -1;
return Math.max(left,right)+1;
}
}