题解 | #链表内指定区间反转#

核心思路主要是借助临时头结点，找到需要翻转链表的前驱位置，然后将要翻转链表的节点摘下进行子链表的头部插入即可

struct ListNode* reverseBetween(struct ListNode* head, int m, int n ) {
    if (head == NULL || head->next == NULL || m == n)
        return head;

    //借助临时头结点，可以统一所有的情况进行处理，尤其是翻转的链表从第一个节点开始
    struct ListNode* new_head = (struct ListNode*)malloc(sizeof(struct ListNode));
    new_head->next = head;

    //pre指向翻转子链表的前驱节点
    struct ListNode* pre = new_head;

    for (int i = 1; i < m; ++i) { //寻找头插位置
        pre = pre->next;
    }

    //head指向翻转子链表的首部
    head = pre->next;
    for (int i = m; i < n; ++i) {
//将p节点摘下进行子链表的头部插入
        struct ListNode* p = head->next;
        head->next = p->next;
        p->next = pre->next;
        pre->next = p;
    }
    head = new_head->next;
    free(new_head);
    return head;
}