题解 | #链表内指定区间反转#
链表内指定区间反转
https://www.nowcoder.com/practice/b58434e200a648c589ca2063f1faf58c
import java.util.*; /* * public class ListNode { * int val; * ListNode next = null; * } */ public class Solution { /** * * @param head ListNode类 * @param m int整型 * @param n int整型 * @return ListNode类 */ public ListNode reverseBetween (ListNode head, int m, int n) { if(head == null || head.next == null || m==n){ return head; } //创建一个虚节点 ListNode dummy = new ListNode(-1); dummy.val = -1; dummy.next = head; //m位置的前一个节点 ListNode ll = dummy,lr ,rl = dummy,rr; for(int i = 0; i< m-1; i++){ ll = ll.next; } //m位置的节点 lr = ll.next; //n位置的节点 for(int i = 0; i< n; i++){ rl = rl.next; } //n后一个节点 rr = rl.next; rl.next = null; reverse(lr); //把反转后的连接起来 ll.next = rl; lr.next = rr; return dummy.next; } public static void reverse(ListNode head){ if(head == null){ return; } ListNode pre = null, cur = head; while(cur != null){ ListNode tmp = cur.next; cur.next = pre; pre = cur; cur = tmp; } } }