LeetCode 83.Remove Duplicates from Sorted List 刪除排序鏈表中的重複元素

題目描述

給定一個排序鏈表，刪除所有重複的元素，使得每個元素只出現一次。

示例 1:

輸入: 1->1->2
輸出: 1->2
示例 2:

輸入: 1->1->2->3->3
輸出: 1->2->3

來源：力扣（LeetCode）
鏈接：https://leetcode-cn.com/problems/remove-duplicates-from-sorted-list

思路

遞歸

迭代

c++

// 迭代
/** 
 * 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) {
        ListNode real_head(-1);
        real_head.next = head;
        ListNode *p = &real_head, *q = head;
        while(q){
            while(q -> next && q -> next -> val == q -> val) 
                q = q -> next;
            if(p -> next == q) 
                p = q;
            else {
                p ->next = q;
                p = p->next;
            }
            q = q -> next;
        }
        return real_head.next;
    }
}; 

class Solution {
public:
    ListNode* deleteDuplicates(ListNode* head) {
         if (head == nullptr)    return nullptr;
        ListNode *p = head;
        while(p->next != nullptr && p->val == p->next->val)
            p = p->next;
        if(head == p){
            head->next =  deleteDuplicates(head->next);
            return head;
        }
        else
            return deleteDuplicates(head->next);
    }   
};