83. Remove Duplicates from Sorted List

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.

递归搞一下，链表这种东西使用递归会很方便

/**
 * 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 * p = head;
        if (head == NULL) return NULL;
        head->next = deleteDuplicates(head->next);
        if(head->next != NULL && head->val == head->next->val) head = head->next;
        return head;
    }
};