19.2.21 [LeetCode 82] Remove Duplicates from Sorted List II

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

Example 1:

Input: 1->2->3->3->4->4->5
Output: 1->2->5

Example 2:

Input: 1->1->1->2->3
Output: 2->3

题意

如果链表中有一个数重复了，去掉所有这个数

题解

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        ListNode*last = head, *p = head, *ans = new ListNode(0), *now = ans;
        if (!p||p->next==NULL)return head;
        p = p->next;
        bool flag = false;
        while (p) {
            if (last->val != p->val) {
                if (flag == false) {
                    now->next = last; now = now->next;
                    last = p, p = p->next;
                }
                else
                    last = last->next, p = p->next;
                flag = false;
            }
            else {
                flag = true;
                last = last->next, p = p->next;
            }
        }
        if(flag)
            now->next = NULL;
        else now->next = last;
        return ans->next;
    }
};