Question Definition
Reverse a linked list from position m to n. Do it in-place and in one-pass.
For example: Given 1->2->3->4->5->NULL, m = 2 and n = 4,
return 1->4->3->2->5->NULL.
Note:
Given m, n satisfy the following condition: 1 ≤ m ≤ n ≤ length of list.
Java Solution
public ListNode reverseBetween(ListNode head, int m, int n) {
ListNode dummy = new ListNode(-1);
dummy.next = head;
ListNode cur = dummy;
ListNode pre = null;
ListNode front = null;
ListNode last = null;
for (int i = 1; i <= m - 1; ++i) cur = cur.next;
pre = cur;
last = cur.next;
for (int i = m; i <= n; ++i) {
cur = pre.next;
pre.next = cur.next;
cur.next = front;
front = cur;
}
cur = pre.next;
pre.next = front;
last.next = cur;
return dummy.next;
}
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