leetcode解题: Remove Duplicates from Sorted List (83)

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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.

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解法1：Two pointers O(N)

用双指针，比较两node的值，如果相等，则前面的指针跳过下一个node（删除后一个node）。如果不相等，则两个指针同时向后移动直到尾部。
C++

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/**
 * 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 == NULL || head->next == NULL) {
            return head;
        }
        ListNode* res = head;
        ListNode* ptr = head->next;
        while (ptr != NULL) {
            if (head->val == ptr->val) {
                ListNode* temp = ptr;
                head->next = ptr->next;
                delete temp;
                ptr = head->next;
            } else {
                head = head->next;
                ptr = ptr->next;
            }
        }
        return res;
    }
};

Java

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