[LeetCode]Remove Duplicates from Sorted List II

题目描述:(链接)

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.

解题思路:

递归版:

/**
 * 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 || !(head->next)) return head;
        
        ListNode *p = head->next;
        if (head->val == p->val) {
            while (p && head->val == p->val) {
                ListNode *tmp = p;
                p = p->next;
                delete tmp;
            }
            delete head;
            return deleteDuplicates(p);
        } else {
            head->next = deleteDuplicates(head->next);
            return head;
        }
    }
};

 迭代版:2015-10-27

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
        if (!head || !(head->next)) return head;
        
        ListNode dummy(-1);
        ListNode *prev = &dummy;
        ListNode *cur = head;
        bool isDuplicated = false;
        while (cur != nullptr) {
            isDuplicated = false;
            while (cur->next != nullptr && cur->val == cur->next->val) {
                isDuplicated = true;
                cur = cur->next;
            }
            
            if (isDuplicated) {
                cur = cur->next;
                continue;
            }
            
            prev->next = cur;
            prev = prev->next;
            cur = cur->next;
            
        }
        
        prev->next = cur;
        
        return dummy.next;
    }
};