面试题06. 从尾到头打印链表

题目：

 

 

解答：

方法一：栈保存，先进后出。

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     vector<int> reversePrint(ListNode* head) 
12     {
13         vector<int> res;
14         std::stack<int> st;
15 
16         if (NULL == head)
17         {
18             return res;
19         }
20 
21         while (head != NULL)
22         {
23             st.push(head->val);
24             head = head->next;
25         }
26 
27         while (!st.empty())
28         {
29             res.push_back(st.top());
30             st.pop();
31         }
32 
33         return res;
34     }
35 };

 

方法二：反转链表，然后在进行遍历。

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11 
12     ListNode * reverse(ListNode *head)
13     {
14         if (NULL == head || NULL == head->next)
15         {
16             return head;
17         }
18 
19         ListNode *p1;
20         ListNode *p2;
21         ListNode *p3;
22 
23         p1 = head;
24         p2 = head->next;
25 
26         while (p2 != NULL)
27         {
28             p3 = p2->next;
29             p2->next = p1;
30             p1 = p2;
31             p2 = p3;
32         }
33 
34         head->next = NULL;
35         head = p1;
36 
37         return head;
38     }
39 
40     vector<int> reversePrint(ListNode* head) 
41     {
42         vector<int> res;
43         
44         if (NULL == head)
45         {
46             return res;
47         }
48 
49         ListNode *new_head = reverse(head);
50 
51         while (new_head != NULL)
52         {
53             res.push_back(new_head->val);
54             new_head = new_head->next;
55         }
56 
57         return res;
58     }
59 };

 

方法三：递归

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     vector<int> res;
12     vector<int> reversePrint(ListNode* head) 
13     {
14         if(head == nullptr)
15         {
16             return res;
17         }
18         reversePrint(head->next);
19         res.push_back(head->val);
20         return res;
21     }
22 };

 

posted @ 2020-05-09 12:28  梦醒潇湘  阅读(157)  评论(0)    收藏  举报