I am trying to solve leetcode problem in Go to teach myself the language. I have a single linked list and an insert function:
type ListNode struct {
Val int
Next * ListNode
}
func Insert(listNode * ListNode, i int) {
// @fixme how to check the first node?
if listNode == nil {
listNode.Val = i
listNode.Next = nil
} else {
for;;
listNode = listNode.Next {
if listNode.Next == nil {
listNode.Next = & ListNode {
i, nil
}
break
}
}
}
}
func main() {
vals: = [] int {
1, 2, 3, 4, 5
}
var list ListNode
for _,
i: = range vals {
Insert( & list, i)
}
}
The problem is that when an instance of ListNode is instantiated the struct fields have zero values and I am unable update the set first element of the list because I am unable to check for it. In other words, that a ListNode item is initialized but empty. So when I want build a list 1->2->3->4->5 I end up having: 0->1 ->2 ...5 . The limitation is that I cannot change the struct definition as leetcode have that already defined. Here is a working example of the code above: https://play.golang.org/p/bIz-VjY1PS7
What you should do is that you shouldn't use ListNode you should be using *ListNode, that way an empty list is represented by a nil *ListNode:
func New() *ListNode {
return nil
}
func Insert(listNode *ListNode, i int) *ListNode {
// If it's nil, create it
if listNode == nil {
listNode = &ListNode{i, nil}
} else {
l := listNode
for ; l.Next != nil; l = l.Next {
}
l.Next = &ListNode{i, nil}
}
return listNode
}