[LeetCode]Remove Duplicates from Sorted List

题目描述:(链接）

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.

解题思路：

/**
 * 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 *prev = NULL;
        for (ListNode *cur = head; cur != NULL; cur = cur->next) {
            if (cur == head) {
                prev = cur;
                continue;
            }
            
            if (cur->val == prev->val) {
                prev->next = cur->next;
            } else {
                prev = cur;
            }
        }
        
        return head;
    }
};

 递归版:2015-10-26更新

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