[LeetCode]61. Rotate List

61. Rotate List

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:Given 1->2->3->4->5->NULL and k = 2,return 4->5->1->2->3->NULL.

分析

链表旋转问题，不像数组容易知道数组长度，链表只能先遍历一次，找到长度，然后再找到倒数第k-1个节点，然后重组链表

源码

/** * Definition for singly-linked list. * struct ListNode { *     int val; *     ListNode *next; *     ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public:    ListNode* rotateRight(ListNode* head, int k) {        if(!head || head->next == NULL) return head;        // 统计链表长度，并记录最后一个节点pLast        ListNode *pNode = head, *pLast = NULL;        int count = 0;        while(pNode){            count++;            pLast = pNode;            pNode = pNode->next;        }        // k可能大于count，长度取模值        k = k % count;        if(k == 0) return head; // k是链表长度的整数倍时直接返回        // 找到第m-k个节点        int m = count - k - 1;        int i = 0;        pNode = head;        while(i < m) {            i++;            pNode = pNode->next;        }        // 连接链表        pLast->next = head;        head = pNode->next;        pNode->next = NULL;        return head;    }};