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public class ReverseLinkedListII {
public ListNode reverseBetween(ListNode head, int m, int n) {
if (head == null || head.next == null) {
return head;
}
int length = 0;
ListNode cursor = head;
while (cursor != null) {
length++;
cursor = cursor.next;
}
if (m >= length) {
return head;
}
ListNode preHead = new ListNode(0);
preHead.next = head;
ListNode pre = preHead;
int count = n - m + 1;
while (m > 1) {
pre = pre.next;
m--;
}
cursor = pre.next;
List<ListNode> list = new ArrayList<ListNode>();
while (count > 0 && cursor != null) {
list.add(cursor);
count--;
cursor = cursor.next;
}
for (int i = list.size() - 1; i >= 0; i--) {
pre.next = list.get(i);
pre = pre.next;
}
pre.next = cursor;
return preHead.next;
}
@Test
public void test() {
ListNode head = new ListNode(1);
head.next = new ListNode(2);
head.next.next = new ListNode(3);
head.next.next.next = new ListNode(4);
head.next.next.next.next = new ListNode(5);
ListNode result = reverseBetween(head, 1, 4);
}
}
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