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.
public ListNode reverseBetween(ListNode head, int m, int n) { // Start typing your Java solution below // DO NOT write main() function if(m == n) return head; ListNode pBefore = new ListNode(-1); pBefore.next = head; ListNode prev, curr = head,next; int c = 1; while(c < m){ pBefore = pBefore.next; c++; } ListNode mNode = pBefore.next; prev = pBefore.next; curr = prev.next; while(c < n){ next = curr.next; curr.next = prev; prev = curr; curr = next; c++; } pBefore.next = prev; mNode.next = curr; return mNode == head ? pBefore.next : head; }