Patterns

Iterate with prev/curr/next; flip pointer each step

When to useReverse a list, reverse sub-list, reorder list

iterative

INITIALIZE

prev = null; curr = head

let prev = null;
let curr = head;

let curr = head;
let newHead = null;

TRAVERSE

while (curr !== null)

while (curr !== null) {

while (curr !== null) {

capture next

const next = curr.next

—

[REVERSE]

curr.next = prev (or swap prev/next for doubly-linked)

  curr.next = prev;

  curr.next = curr.prev;
  curr.prev = next;

advance

prev = curr; curr = next

  prev = curr;
  curr = next;

  newHead = curr;
  curr = next;

RETURN

return prev (the new head)

return prev;

return newHead;