[LeetCode] #206. Reverse Linked List

[Easy][Question]: Given the head of a singly linked list, reverse the list, and return the reversed list.

Example 1:

Input: head = [1,2,3,4,5]
Output: [5,4,3,2,1]

Example 2:

Input: head = [1,2]
Output: [2,1]

Example 3:

Input: head = []
Output: []

Constraints:

• The number of nodes in the list is the range [0, 5000].
• -5000 <= Node.val <= 5000

My Solution[C++]:

[Ideas]: 用1->2->3->4->5舉例，用疊代的方式，最後一層為head=4，head->next=5，代入後return5，從最尾巴的地方5變成新的node的頭，再把head -> next -> next = head，意思是4->5->next=4，所以5->4，下一行head -> next = NULL;，4->NULL，以此類推。