package algorithm_practice;

import common.datastruct.ListNode;

import common.util.ConstructListNode;

import common.util.SysOut;

import org.junit.Test;

/**

* Created by nibnait on 2020/11/24

*/

public class TempTest {

@Test

public void testCase() {

ListNode head = ConstructListNode.construct(new int[]{1, 2, 3, 4, 5});

SysOut.printList(head);

head = reverseK(head, 2);

SysOut.printList(head);

}

private ListNode reverseK(ListNode head, int k) {

if (head == null) {

return null;

}

ListNode dummyHead = new ListNode();

dummyHead.next = head;

while (dummyHead.next != null) {

dummyHead.next = reverseN(dummyHead.next, k);

for (int i = 0; i < k; i++) {

if (dummyHead.next == null) {

break;

}

dummyHead = dummyHead.next;

}

}

return dummyHead.next;

}

private ListNode reverseN(ListNode head, int n) {

if (n == 1) {

return head;

}

ListNode last = reverseN(head.next, n-1);

head.next.next = head;

head.next = null;

return last;

}

}