LeetCode Remove Duplicates from Sorted List II

class Solution {
public:
    ListNode *deleteDuplicates(ListNode *head) {
        if (head == NULL || head->next == NULL) return head;
        
        ListNode *tail = NULL, *h = NULL, *cur = head->next;
        ListNode *prev = head;
        
        bool nodup = true;

        while (cur != NULL) {
            if (cur->val != prev->val) {
                if (nodup) {
                    if (h == NULL) {
                        h=tail=prev;
                    } else {
                        tail->next = prev;
                        tail = prev;
                    }
                    tail->next = NULL;
                } else {
                    nodup = true;   // reset the flag
                }
            } else {
                nodup = false;
            }
            prev = cur;
            cur = cur->next;
        }

        if (nodup) {
            if (h == NULL) {
                h = prev;
            } else {
                tail->next = prev;
            }
        }
        return h;
    }
};

需要仔细写啊

第二轮：

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.

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
 // 9:40
class Solution {
public:
    ListNode *deleteDuplicates(ListNode *head) {
        if (head == NULL) {
            return NULL;
        }
        ListNode fakeHead(0);
        ListNode* last = &fakeHead;
        ListNode* cur = head->next;
        ListNode* pre = head;
        int cnt = 1;
        while (cur != NULL) {
            if (cur->val != pre->val) {
                if (cnt == 1) {
                    last->next = pre;
                    last = pre;
                }
                cnt = 1;
            } else {
                cnt++;
            }
            pre = cur;
            cur = cur->next;
        }
        
        if (cnt == 1) {
            last->next = pre;
            last = pre;
        }
        last->next = NULL;
        
        return fakeHead.next;
    }
};