83. Remove Duplicates from Sorted List

• Total Accepted: 163106
• Total Submissions: 417745
• Difficulty: Easy
• Contributors: Admin

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

For example,
Given 1->1->2, return 1->2.
Given 1->1->2->3->3, return 1->2->3.

来源： https://leetcode.com/problems/remove-duplicates-from-sorted-list/

分析

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使用双指针， pre 和 cur，非递归

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/**  * Definition for singly-linked list.  * struct ListNode {  *     int val;  *     ListNode *next;  *     ListNode(int x) : val(x), next(NULL) {}  * };  */ class Solution { public:     ListNode* deleteDuplicates(ListNode* head) {         if(head == NULL || head->next == NULL) return head;                   ListNode* pre = head;         ListNode* cur = head->next;         while(cur != NULL){             if(cur->val == pre->val){                 ListNode * tmp = cur;                 cur = cur->next;                 pre->next = cur;                 delete tmp;             }             else{                 pre = pre->next;                 cur = cur->next;             }         }         return head;     } };

递归法

删除head之后的list中重复元素，

然后再比较，如果head->val == head->next->val

则返回head->next

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class Solution { public:     ListNode* deleteDuplicates(ListNode* head) {          if(head == NULL || head->next == NULL) return head;          head->next = deleteDuplicates(head->next);          if(head->next->val == head->val){             ListNode* tmp = head;             head = head->next;             delete tmp;          }          return head;     } };

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