LeetCode 面试经典150题 [57/150 反转链表II]

题目描述

给你单链表的头指针 head 和两个整数 left 和 right ，其中 left <= right 。请你反转从位置 left 到位置 right 的链表节点，返回 反转后的链表 示例一

输入：head = [1,2,3,4,5], left = 2, right = 4
输出：[1,4,3,2,5]

示例二

输入：head = [5], left = 1, right = 1
输出：[5]

个人C++解答

/**
 * 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 left, int right) {
        stack<int> stk;
        ListNode *result = new ListNode();
        ListNode *p = head;
        int step = 1;
        while(step!=right+1){
            if(step>=left && step<=right){
                stk.push(p->val);
            }
            p = p->next;
            step++;
        }
        step = 1;
        ListNode *q = result;
        while(head!=nullptr){
            if(step>=left && step<=right)
            {
                q->next = new ListNode(stk.top());
                stk.pop();
            }else{
                q->next = head;
            }
            head = head->next;
            q = q->next;
            step++;
        }
        return result->next;
    }
};