#链表 #反转链表

reverse-linked-list.cpp

/**
 * 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* reverseList(ListNode* head) {
        ListNode* pre = NULL;
        ListNode* cur = head;
        ListNode* post;
        while (cur != NULL) {
            post = cur->next;  // save next node
            cur->next = pre;   // inverse list
            pre = cur;         // save the previous node
            cur = post;
        }
        return pre;
    }
};