package main

import (
	"fmt"
)

type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func maxInt(x, y int) int {
	if x > y {
		return x
	}
	return y
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}

func treeDepth(root *TreeNode, depth int) int {
	if root == nil {
		return depth
	}
	return maxInt(treeDepth(root.Left, depth+1), treeDepth(root.Right, depth+1))
}

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func isBalanced(root *TreeNode) bool {
	if root == nil {
		return true
	}
	if abs(treeDepth(root.Left, 0)-treeDepth(root.Right, 0)) > 1 {
		return false
	}
	return isBalanced(root.Left) && isBalanced(root.Right)
}

func main() {
	/**
	 * t1:  5
	 *     / \
	 *    1   4
	 *       / \
	 *      2   3
	 */
	t1l := TreeNode{1, nil, nil}
	t1rl := TreeNode{2, nil, nil}
	t1rr := TreeNode{3, nil, nil}
	t1r := TreeNode{4, &t1rl, &t1rr}
	t1 := &TreeNode{5, &t1l, &t1r}
	fmt.Println(isBalanced(t1))
	fmt.Println(isBalanced(nil))
}