Leetcode 83. Remove Duplicates from Sorted List

最新推荐文章于 2025-09-05 23:16:08 发布

ruihuank

最新推荐文章于 2025-09-05 23:16:08 发布

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本文介绍了一种算法，用于从已排序的链表中移除所有重复元素，确保每个元素只出现一次。提供了两种实现方法：一种是非破坏性的，另一种是在移除重复项时释放内存的方法。

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.

/**
 * 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* first = head;
        ListNode* second = first;

        while (first) {
            if (first->val != second->val) {
                if (second->next != first)
                    second->next = first;
                second = first;
            }
            first = first->next;
        }
        if (second != NULL) second->next = NULL;

        return head;
    }
};

考虑delete

/**
 * 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) return head;

        ListNode* second = head;
        ListNode* first = head->next;

        while (first) {
            if (first->val != second->val) {
                if (second->next != first)
                    second->next = first;
                second = first;
                first = first->next;
            } else {
                ListNode *p = first->next;
                delete first;
                first = p;
            }
        }

        if (second != NULL) {
            second->next = NULL;
        }

        return head;
    }
};