206. Reverse Linked List

Reverse a singly linked list and return the new head.

Walk the list with prev and curr. Save curr.next, point curr back at prev, then move both one step forward.

1function reverseList(head: ListNode | null): ListNode | null {
2  let prev: ListNode | null = null, curr = head;
3  while (curr) {
4    const next = curr.next;
5    curr.next = prev;
6    prev = curr;
7    curr = next;
8  }
9  return prev;
10}

list

curr

→

→ ∅

prev = null, curr = head.

1 / 0

Space: play/pause · ←/→: step