LeetCode 92. Reverse Linked List II

Description

Reverse a linked list from position m to n. Do it in one-pass.
Note: 1 ≤ m ≤ n ≤ length of list.
Example:
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Input: 1->2->3->4->5->NULL, m = 2, n = 4
Output: 1->4->3->2->5->NULL

遍历一次将链表的第m至n个结点翻转。

Solution

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func reverseBetween(head *ListNode, m int, n int) *ListNode {
    slow := &ListNode{
        Next: head,
    }
    fast := slow.Next
    head = slow

    for i := 1; i < m; i++ {
        fast = fast.Next
        slow = slow.Next
    }

    // start指向第一个需要翻转的位置
    pre, start := slow, fast

    // 进行翻转
    // 1. 将fast.Next倒转，指向slow
    // 2. 同时fast和slow前进一步
    for i := m; i <= n; i++ {
        fast.Next, fast, slow = slow, fast.Next, fast
    }

    pre.Next = slow
    start.Next = fast

    return head.Next
}