61.旋转链表

最新推荐文章于 2025-04-02 16:57:31 发布

原创最新推荐文章于 2025-04-02 16:57:31 发布 · 111 阅读

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1 链表转环法

在这里插入图片描述

class Solution {
public:
    ListNode* rotateRight(ListNode* head, int k) {
        if(k == 0 || head == nullptr || head->next == nullptr) return head;//多个特判合到一起
        
        int len = 0;
        ListNode* tmp = head;
        for(;tmp->next!=nullptr;tmp=tmp->next)
            len++;
        // 形成闭环
        tmp->next = head;

        //reduce calculate times
        k = k % (len+1);

        ListNode* stop = head;
        while(k<len) //找到应该断开的位置
        {
            stop = stop->next;
            k++;
        }
        head=stop->next;
        stop->next=nullptr;

    return head;
    }
};

2 穷举法

class Solution {
public:
    ListNode* rotateRight(ListNode* head, int k) {
        if(k == 0 || head == nullptr || head->next == nullptr) return head;//多个特判合到一起
        
        int len = 0;
        for(ListNode* tmp = head;tmp->next!=nullptr;tmp=tmp->next;)
            len++;

        //reduce calculate times
        k = k % (len+1);

        while(k>0)
        {
            ListNode* last2 = head; //last 2
            ListNode* last1 = head->next; //last 1
            
            while(last1->next != nullptr)
            {
                last2 = last1;
                last1 = last1->next;
            }
            
            last1->next = head;
            last2->next = nullptr;
            head = last1;

            k--;
        }
    return head;
    }
};