Leetcode: 83. Remove Duplicates from Sorted List

Description

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

Example

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

思路

• 链表去重，一旦重复，留下一个节点

代码

/**
 * 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) return NULL;
        ListNode *ptr = head, *pNext = head->next;
        ListNode *res = new ListNode(0);
        ListNode *h = res;
        
        while(pNext){
            if(ptr->val == pNext->val){
                do{
                    ListNode *tmp = pNext;
                    pNext = pNext->next;
                    delete tmp;
                }while(pNext && pNext->val == ptr->val);
            }
            
            res->next = ptr;
            res = res->next;
            ptr = pNext;
            if(ptr)
                pNext = ptr->next;
        }
        
        if(ptr && res && res->val != ptr->val){
            res->next = ptr;
            res = res->next;
        }
        
        res->next = NULL;
        return h->next;
    }
};