Ref: 2 step by step diagrams added.

analysis/04-reverse-linked-list/diagrams/00_initial_state.puml

@@ -0,0 +1,35 @@
+@startuml
+title Step 0 — Initial State
+
+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
+
+prev --> "null"
+cur --> n1
+
+note bottom
+Before the loop starts:
+
+previous = null
+current  = head
+
+The original list is still intact.
+end note
+
+@enduml