Golang Leetcode 653. Two Sum IV - Input is a BST.go

var m map[int]bool

func helper(root *TreeNode, k int) bool {
	if root == nil {
		return false
	}
	if _, ok := m[k-root.Val]; ok {
		return true
	}
	m[root.Val] = true
	return helper(root.Left, k) || helper(root.Right, k)
}
func findTarget(root *TreeNode, k int) bool {
	m = make(map[int]bool)
	return helper(root, k)
}