Leetcode: remove duplicates from sorted list

Leetcode: remove duplicates from sorted list

Given a sorted Linked List, delete all duplicates such that each element appear onlyOnce.

For example,
Given1->1->2, Return1->2.
Given1->1->2->3->3, Return1->2->3.

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

Algorithm: No problem. Check the Code directly:

 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 || head->next == NULL) return head;13         ListNode *p = head;14         while(p->next){15             if(p->next->val == p->val){16                 ListNode *q = p->next;17                 p->next = q->next;18                 free(q);19             }else{20                 p = p->next;21             }22         }23         return head;24     }25 };

Question 2:

Given a sorted Linked List, delete all nodes that have duplicate numbers, leaving onlyDistinctNumbers from the original list.

For example,
Given1->2->3->3->4->4->5, Return1->2->5.
Given1->1->1->2->3, Return2->3.

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

Algorithm: This question is a little more difficult than the above question, but it is not very difficult. Code:

 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 || head->next == NULL) return head;13         ListNode *pre = NULL;14         ListNode *p = head;15         while(p){16             ListNode *q = p->next;17             while(q && q->val == p->val){18                 q = q->next;19             }20             if(p->next == q){21                 pre = p;22                 p = p->next;23             }else{24                 if(pre){25                     pre->next = q;26                 }else{27                     head = q;28                 }29                 while(p != q){30                     ListNode *tempP = p->next;31                     free(p);32                     p = tempP;33                 }34                 p = q;35             }36         }37         return head;38     }39 };

 

Leetcode: remove duplicates from sorted list