LEET code -- Reverse Linked List

Reverse a singly linked list.

反轉link list
用指標 跑一圈就可以
要注意回傳的是pre  不是ret
因為ret停止地方會是NULL

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/** * Definition for singly-linked list. * struct ListNode { * int val; * struct ListNode *next; * }; */ struct ListNode* reverseList(struct ListNode* head) { struct ListNode* pre=NULL,*ret=head,*frn; while(ret!=NULL){ frn=ret->next; ret->next=pre; pre=ret; ret=frn; } return pre; }