92 Reverse Linked List II

从m到n位，对于链表进行反转

Python

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def reverseBetween(self, head, m, n):
        """
        :type head: ListNode
        :type m: int
        :type n: int
        :rtype: ListNode
        """
        dummy = ListNode(-1)
        dummy.next = head
        pre = dummy
        for i in range(m-1):
            pre = pre.next
        cur = pre.next
        for i in range(m, n):
            t = cur.next
            cur.next = t.next
            t.next = pre.next
            pre.next = t
        return dummy.next

Java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode reverseBetween(ListNode head, int m, int n) {
        ListNode fakeHead = new ListNode(-1);
        fakeHead.next = head;
        ListNode prev = fakeHead;
        for(int i = 0; i < m - 1; i ++){
            prev = prev.next;
        }
        ListNode curr = prev.next;
        for(int i = m; i < n; i ++){
            ListNode t = curr.next;
            curr.next = t.next;
            t.next = prev.next;
            prev.next = t;
        }
        return fakeHead.next;
    }
}