Leetcode 203. Remove Linked List Elements

文章作者：Tyan
博客：noahsnail.com  |  CSDN  |  简书

1. Description

2. Solution

• Version 1

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        if(!head) {
            return nullptr;
        }
        ListNode* start = new ListNode(0);
        start->next = head;
        ListNode* pre = start;
        ListNode* current = head;
        while(current) {
            if(current->val == val) {
                pre->next = current->next;
            }
            else {
                pre = pre->next;
            }
            current = current->next;
        }
        return start->next;
    }
};

• Version 2

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        if(!head) {
            return nullptr;
        }
        head->next = removeElements(head->next, val);
        if(head->val == val) {
            return head->next;
        }
        return head;
    }
};

Reference

1. https://leetcode.com/problems/remove-linked-list-elements/description/