I、Given a sorted linked list, delete all duplicates such that each element appear only once.

For example,

Given1->1->2, return1->2.

Given1->1->2->3->3, return1->2->3.

 

PS：遍历，而后记录pre，并删除后续重复node

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     ListNode *deleteDuplicates(ListNode *head) {12         ListNode *cur=head,*pre=NULL;13         while(cur!=NULL){14             if(pre==NULL){15                 pre=cur;16                 cur=cur->next;17                 continue;18             }19             ListNode *next=cur->next;20             if(pre->val==cur->val){21                 pre->next=next;22             }else23                 pre=cur;24             cur=next;25         }26         return head;27     }28 };

II、

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,

Given1->2->3->3->4->4->5, return1->2->5.

Given1->1->1->2->3, return2->3.

 

删除所有重复项。

PS：循环比较next->val==cur->val，若next跳动则剔除cur至next之间的节点。否则右移left指针。

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     ListNode *deleteDuplicates(ListNode *head) {12         if(head==NULL) return NULL;13         ListNode h(-1);14         ListNode *res=&h;15         res->next=head;16         ListNode *cur=head,*pre=NULL,*left=res;17         while(cur!=NULL){18             ListNode* next=cur->next;19             while(next!=NULL&&cur->val==next->val){20                 next=next->next;21             }22             if(next==cur->next){23                 left=cur;24             }else{25                 left->next=next;26             }27             cur=next;28         }29         return res->next;30     }31 };