3 months ago
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花 风 城市




  • 时间复杂度:O(2n) = O(n)
  • 空间复杂度:因为递归次数大概是n / k,所以O(n / k)
public ListNode reverseKGroup(ListNode head, int k) {
if (head == null || head.next == null) return head;
ListNode tail = head;
for (int i = 0; i < k; i++) {
if (tail == null) return head;
tail = tail.next;
ListNode newHead = reverse(head, tail);
head.next = reverseKGroup(tail, k);
return newHead;
private ListNode reverse(ListNode head, ListNode tail) {
ListNode pre = null;
ListNode next = null;
while (head != tail) {
next = head.next;
head.next = pre;
pre = head;
head = next;
return pre;

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