The idea is simple and intuitive: find linkedlist [m, n], reverse it, then connect m with n+1, connect n with m-1
class Solution: # @param head, a ListNode # @param m, an integer # @param n, an integer # @return a ListNode def reverseBetween(self, head, m, n): if m == n: return head dummyNode = ListNode(0) dummyNode.next = head pre = dummyNode for i in range(m - 1): pre = pre.next # reverse the [m, n] nodes reverse = None cur = pre.next for i in range(n - m + 1): next = cur.next cur.next = reverse reverse = cur cur = next pre.next.next = cur pre.next = reverse return dummyNode.next
@IWantToPass pre.next refers to the end of the reversed list (first prev = None), pre.next.next links it to the latter part of the none reversed list.(1-->2, 2-->5)
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