leetCode.92. 反转链表 II

题目思路

代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* reverseBetween(ListNode* head, int m, int n) {
        auto dummy = new ListNode( -1 );
        dummy->next = head;

        auto a = dummy;
        for ( int i = 0; i < m - 1; ++ i ) a = a->next;
        auto b = a->next;
        auto c = b->next;

        for ( int i = 0; i < n - m; ++ i ) {
            auto t = c->next;
            c->next = b;
            b = c;
            c = t;
        }

        a->next->next = c;
        a->next = b;

        return dummy->next;
    }
};