day38（12.19）——leetcode面试经典150

92. 反转链表 II

92. 反转链表Ⅱ

题目：

题解：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseBetween(ListNode head, int left, int right) {
        ListNode cur = head;
        ListNode part = new ListNode();
        int count = 1;
        Map<Integer, ListNode> map = new HashMap<>();
        while(cur != null) {
            map.put(count++, new ListNode(cur.val));
            cur = cur.next;
        } 
        cur = new ListNode();
        ListNode h = cur;
        for(int i=1;i<left;i++) {
            cur.next = map.get(i);
            cur = cur.next;
        }
        for(int i=right;i>=left;i--) {
            cur.next = map.get(i);
            cur = cur.next;
        }
        for(int i=right+1;i<count;i++) {
            cur.next = map.get(i);
            cur = cur.next;
        }
        return h.next;
    }
}