[leetcode] Rotate List

Rotate List

/** Definition for singly-linked list. */

#include <iostream>
using namespace std;

struct ListNode {
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};

class Solution {
public:
    ListNode *rotateRight(ListNode *head, int k) {
        if (head==NULL||k<=0) {
            return head;
        }
        
        //求length
        ListNode *p=head;
        ListNode *pEnd=p;//pEnd指向最后一个非NULL节点
        int length=0;
        while (p!=NULL) {
            length++;
            pEnd=p;
            p=p->next;
        }
        ListNode *pCur=head;
        ListNode *firstEnd=NULL;
        
        int startCur=length-k%length;//开始移动的位置
        //边界条件
        if (k%length==0||length==1) {
            return head;
        }
        //找到第一段结尾处
        while (startCur) {
            firstEnd=pCur;
            pCur=pCur->next;
            startCur--;
        }
        
        pEnd->next=head;
        firstEnd->next=NULL;
        
        return pCur;
        
    }
};

int main(){
    ListNode *p=new ListNode(1);
    p->next=new ListNode(2);
    int k=1;
    Solution so;
    ListNode *res= so.rotateRight(p, k);
    cout<<res->val<<res->next->val<<endl;
}