Leetcode44: Reverse Linked List

Reverse a singly linked list.

定义3个相邻的指针，pre、cur、post，每次往后挪一位，将cur的next指向pre，直到post为空。

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head) {
        if(head == NULL || head->next == NULL)
            return head;

        ListNode* pre = head;
        ListNode* cur = pre->next;
        ListNode* post = cur->next;

        pre->next = NULL;
        while(post)
        {
            cur->next = pre;
            pre = cur;
            cur = post;
            post = post->next;
        }
        cur->next = pre;
        return cur;
    }

};

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