Leetcode 92 Reverse Linked List II

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.

要求在1*n时间内完成

类似于Leetcode 206 Reverse Linked List

保存指针指向倒置链表段的前一个node，在倒置结束后连接其下一个node。

var reverseBetween = function(head, m, n) {
    if(m===n) return head
    var dummy = new ListNode()
    dummy.next = head
    var p = dummy
    for(var i=0;i<m-1;i++) 
        p = p.next
    var c = p.next
    var r = null
    for(var i=0;i<n-m+1;i++){
        var nextnode = c.next
        c.next = r
        r = c
        c = nextnode
    }
    p.next.next = c
    p.next = r
    return dummy.next
}