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오늘은 leet code를 두 문제 풀었습니다

leet code: 1207 - Remove Linked List Elements

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        ListNode* newHead = new ListNode();
        newHead->next = head;
        ListNode* n1 = newHead;
        ListNode* n2 = newHead->next;

        while (n2 != nullptr)
        {
            if (n2->val == val)
            {
                n1->next = n2->next;
                n2 = n1->next;
            }
            else
            {
                n1 = n1->next;
                if (n1 != nullptr)
                    n2 = n1->next;
            }
        }
        return newHead->next;
    }
};

leet code: 1208 - Odd Even Linked List

image-20210503223519374

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* oddEvenList(ListNode* head) {
        ListNode* head1 = new ListNode();
        ListNode* head2 = new ListNode();

        ListNode* ptr1 = head1;
        ListNode* ptr2 = head2;

        int cnt=0;
        while(head!=nullptr)
        {
            if(cnt%2==0)
            {
                ptr1->next = new ListNode(head->val);
                ptr1 = ptr1->next;
            }else
            {
                ptr2->next = new ListNode(head->val);
                ptr2 = ptr2->next;
            }
            head = head->next;
            cnt++;
        }
        ptr1->next = head2->next;
        return head1->next;

    }
};