package main

import (
	"fmt"
)

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

// important!! "leaf node"
func hasPathSumIter(root *TreeNode, sum int, tmpSum int) bool {
	if root.Left == nil && root.Right == nil {
		return tmpSum+root.Val == sum
	}
	if root.Left == nil {
		return hasPathSumIter(root.Right, sum, tmpSum+root.Val)
	}
	if root.Right == nil {
		return hasPathSumIter(root.Left, sum, tmpSum+root.Val)
	}
	return hasPathSumIter(root.Left, sum, tmpSum+root.Val) || hasPathSumIter(root.Right, sum, tmpSum+root.Val)
}

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func hasPathSum(root *TreeNode, sum int) bool {
	if root == nil {
		return false
	}
	return hasPathSumIter(root, sum, 0)
}

func main() {
	/**
	 * t1:  5
	 *     / \
	 *    1   4
	 *       / \
	 *      2   3
	 */
	t1r := TreeNode{4, nil, nil}
	t1 := &TreeNode{5, nil, &t1r}
	fmt.Println(hasPathSum(t1, 11))
	fmt.Println(hasPathSum(t1, 5))
	fmt.Println(hasPathSum(t1, 7))
	fmt.Println(hasPathSum(nil, 0))
}