题解 | 链表内指定区间反转 试读

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 *	ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
/**
 * struct ListNode {
 *    int val;
 *    struct ListNode *next;
 *    ListNode(int x) : val(x), next(nullptr) {}
 * };
 */
class Solution {
public:
    ListNode* reverseBetween(ListNode* head, int m, int n) {
        if (head == nullptr || m == n) return head;
        
        ListNode* dummy = new ListNode(0);
        dummy->next = head;
        ListNode* pre = dummy;
        
        for (int i = 1; i < m; i++) {
            pre = pre->next;
        }
        
        ListNode* start = pre->next;
        ListNode* then = start->next;
        
        for (int i = 0; i < n - m; i++) {
            start->next = then->next;
            then->next = pre->next;
            pre->next = then;
            then = start->next;
        }
        
        ListNode* result = dummy->next;
        delete dummy;
        return result;
    }
};