82. Remove Duplicates from Sorted List II

• Total Accepted: 97678
• Total Submissions: 339601
• Difficulty: Medium
• Contributors: Admin

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

For example,
Given 1->2->3->3->4->4->5, return 1->2->5.
Given 1->1->1->2->3, return 2->3.

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

分析

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使用三个指针

pre, cur, sub

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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 dummy(0);         ListNode* pre = &dummy;         ListNode* cur = head;         dummy.next = head;         while(cur != NULL && cur->next != NULL){             //sub record the first node tha differ with cur             ListNode* sub = cur->next;             while(sub != NULL && cur->val == sub->val){                 sub = sub->next;             }                           if(cur->next != sub){                 pre->next = sub;                 deleteList(cur, sub);                 cur = sub;             }             else{                 pre = cur;                 cur = cur->next;             }         }         return dummy.next;     }           void deleteList(ListNode* head, ListNode* end){         while(head != end){             ListNode* d = head;             head = head->next;             delete d;         }     } };

使用递归方法

找到最接近的unique的node，对之后的进行delete

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class Solution { public:     ListNode* deleteDuplicates(ListNode* head) {         if(head == NULL || head->next == NULL) return head;                   ListNode* p = head->next;         if(head->val != p->val){             head->next = deleteDuplicates(p);             return head;         }         else{             while(p != NULL && p->val == head->val) p = p->next;             return deleteDuplicates(p);         }               } };

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