BM2『链表内指定区间反转』学习笔记

划分成BM1的子结构问题是最容易理解的

代码片段:

        dummy = ListNode(-2000)
        dummy.next = head
        curr = dummy
        for _ in range(m - 1):
            curr = curr.next
        n0 = curr
        pre = None
        curr = n0.next
        for _ in range(n - m + 1):
            # 这里完全是你 BM1 写过的 4 行标准反转代码
            archive = curr.next
            curr.next = pre
            pre = curr
            curr = archive
        n0.next.next = curr
        n0.next = pre
        return dummy.next