题解 | 链表内指定区间反转

/**
 * struct ListNode {
 *  int val;
 *  struct ListNode *next;
 *  ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param head ListNode类
     * @param m int整型
     * @param n int整型
     * @return ListNode类
     */
    ListNode* reverseBetween(ListNode* head, int m, int n) {
        // write code here
        auto* res = new ListNode(-1);
        res->next = head;

        ListNode* left = res;
        ListNode* cur = head;

        for(int i = 1; i < m; i ++){
            left = cur;
            cur = cur->next;
        }

        for(int i = m; i < n; i ++){
            ListNode* temp = cur->next;
            cur->next = temp->next;
            temp->next = left->next;
            left->next = temp;
        }
        return res->next;

    }
};