链表

反转链表

function reverseList(head: ListNode | null): ListNode | null {
  let pre = null, cur = head

  while (cur) {
    const temp = cur.next
    cur.next = pre
    pre = cur
    cur = temp
  }

  return pre
};

反转链表 II

function reverseBetween(head: ListNode | null, left: number, right: number): ListNode | null {
  const dummyNode = new ListNode(-1, head)

  let pre = dummyNode
  for (let i = 0; i < left - 1; i++) {
    pre = pre.next
  }

  let rightNode = pre
  for (let i = 0; i < right - left + 1; i++) {
    rightNode = rightNode.next
  }

  const leftNode = pre.next
  let last = rightNode.next

  pre.next = null;
  rightNode.next = null;
  reverse(leftNode)

  pre.next = rightNode
  leftNode.next = last

  return dummyNode.next
};

function reverse(head: ListNode) {
  let pre = null, cur = head

  while (cur) {
    const next = cur.next
    cur.next = pre
    pre = cur
    cur = next
  }
}