83. Remove Duplicates from Sorted List 从链表中删去数值重复节点

83. Remove Duplicates from Sorted List

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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.

 

pre指针在后

cur向前扫，扫到不重复的就让节点和pre指向的ListNode连在一起，扫到重复的就继续扫，直到不重复的时候，再和pre指向的ListNode连接

效果是：重新连了一遍，扔掉了重复的节点

/**
 * 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) {
                cur=cur->next;
            }else{
                pre->next=cur;
                pre=cur;
                cur=cur->next;
            }
        }
        pre->next=NULL;
        return head;
    }
};