题解 | #链表内指定区间反转#

/**
 * struct ListNode {
 *	int val;
 *	struct ListNode *next;
 * };
 */

class Solution {
public:
    /**
     * 
     * @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
        if(m >= n || n <= 1){
            cout<<"1\n";
            return head;
        }
        if(m > 1){
            //cout<<"A\n------------------\n";
            ListNode * leftHead = head;
            ListNode * temp = head;
            ListNode * leftTail = nullptr;
            int i = 1;
            while(temp && i++ < m){
                //cout<<"Aaaa\n------------------\n";
                leftTail = temp;
                temp = temp->next; 
            }
            ListNode * tempHead = nullptr;
            ListNode * tempTail = nullptr;
            ListNode * midTail = temp;
            while(temp && m++ <= n){
                //cout<<"Abbb\n------------------\n";
                tempHead = temp;
                temp = temp->next;
                tempHead->next = tempTail;
                tempTail = tempHead;
        }
            leftTail->next = tempTail;
            midTail->next = temp;
            return leftHead;
        }
        else if(m == 1){
            //cout<<"B\n------------------\n";
            ListNode * leftHead = nullptr;
            ListNode * temp = head;
            ListNode * leftTail = nullptr;
            ListNode * newTail = temp;
            while(temp && m++ <= n){
                leftHead = temp;
                temp = temp->next;
                leftHead->next = leftTail;
                leftTail = leftHead;
            }
            newTail->next = temp;
            return leftHead;
        }
        else{
            //cout<<"C\n------------------\n";
            return nullptr;
        }
        return nullptr;
    }
};