import java.util.List;

/*

110 Balanced Binary Tree 32.0% Easy

Problem: Balanced Binary Tree

Difficulty: Easy

Source: https://oj.leetcode.com/problems/balanced-binary-tree/

Notes:

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.

Solution: DFS.

*/

/**

* Definition for binary tree

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode(int x) { val = x; }

* }

*/

public class BalancedBinaryTree {

public boolean isBalanced(TreeNode root) {

if (root == null) return true;

return isBalancedRe(root) > -1;

}

public int isBalancedRe(TreeNode root) {

if (root == null) return 0;

int left = isBalancedRe(root.left);

int right = isBalancedRe(root.right);

if (left == -1 || right == -1) return -1;

if (Math.abs(left - right) > 1) return -1;

return Math.max(left, right) + 1;

}

public static void main(String[] args) {

// TODO Auto-generated method stub

TreeNode t1 = new TreeNode(3);

TreeNode t2 = new TreeNode(9);

TreeNode t3 = new TreeNode(20);

TreeNode t4 = new TreeNode(15);

TreeNode t5 = new TreeNode(7);

t1.left = t2;

t1.right = t3;

t3.left = t4;

t3.right = t5;

BalancedBinaryTree slt = new BalancedBinaryTree();

System.out.print(slt.isBalanced(t1));

}

}