25. K个一组翻转链表
遇到困难直接看题解 --_--,每k个一组,进行翻转,然后再装回原链表中。
class Solution {
public ListNode reverseKGroup(ListNode head, int k) {
ListNode hair = new ListNode(0); //头结点
hair.next = head;
ListNode pre = hair;
while (head != null) {
ListNode tail = pre;
//长度小于k时直接返回
for (int i = 0 ; i < k; i++) {
tail = tail.next;
if (tail == null)
return hair.next;
}
ListNode nex = tail.next;
ListNode[] reverse = myReverse(head,tail);
head = reverse[0];
tail = reverse[1];
//子链表装回原链表
pre.next = head;
tail.next = nex;
pre = tail;
head = tail.next;
}
return hair.next;
}
public ListNode[] myReverse(ListNode head, ListNode tail) {
ListNode prev = tail.next;
ListNode p = head;
while(prev != tail) {
ListNode nex = p.next;
p.next = prev;
prev = p;
p = nex;
}
return new ListNode[] {tail, head};
}
}