06. 從尾到頭打印鏈表

2020-06-22

1.題目描述

輸入一個鏈表的頭節點，從尾到頭反過來返回每個節點的值（用數組返回）。

2.題解

1.放入vector中，然後reverse
2.將鏈表反轉

3.代碼

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> reversePrint(ListNode* head) {
        vector<int>tmp;
        ListNode* p=head;
        while (p){
            tmp.push_back(p->val);
            p=p->next;
        }
        reverse(tmp.begin(),tmp.end());
        return tmp;
    }
};

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> reversePrint(ListNode* head) {
        if (!head) return vector<int>(0);
        vector<int>tmp;
        ListNode* pre=head,*p=pre->next,*t;
        pre->next=NULL;
        while (p){
            t=p->next;
            p->next=pre;
            pre=p;
            p=t;
        }
        while (pre){
            tmp.push_back(pre->val);
            pre=pre->next;
        }
        return tmp;
    }
};