LeetCode/go/insert-greatest-common-divisors-in-linked-list.go

package main

func insertGreatestCommonDivisors(head *ListNode) *ListNode {
	gcd := func(x, y int) int {
		for y != 0 {
			x, y = y, x%y
		}
		return x
	}
	emplace := func(n *ListNode) *ListNode {
		if n.Next == nil {
			return n.Next
		}

		mid := ListNode{
			Val:  gcd(n.Val, n.Next.Val),
			Next: n.Next,
		}
		n.Next = &mid

		return n.Next.Next
	}

	for node := head; node != nil; {
		node = emplace(node)
	}

	return head
}