@startuml
title Step 1 — Save next

object "Node 1" as n1 {
  value = 1
}

object "Node 2" as n2 {
  value = 2
}

object "Node 3" as n3 {
  value = 3
}

n1 --> n2 : next
n2 --> n3 : next
n3 --> "null" : next

object "previous" as prev
object "current" as cur
object "next" as nxt

prev --> "null"
cur --> n1
nxt --> n2

note right of nxt
next = current->next

We save the next node before changing
current->next.

Without this temporary pointer, the rest
of the original list would become unreachable.
end note

@enduml