[LeetCode] 876. Middle of the Linked List [JAVA(자바)]

문제 👉 <Middle of the Linked List - LeetCode>

1. 문제 (링크드리스트의 중간)

링크드리스트의 중간을 반환하라.

Input: [1,2,3,4,5]
Output: Node 3 from this list (Serialization: [3,4,5])
The returned node has value 3.  (The judge's serialization of this node is [3,4,5]).
Note that we returned a ListNode object ans, such that:
ans.val = 3, ans.next.val = 4, ans.next.next.val = 5, and ans.next.next.next = NULL.

Input: [1,2,3,4,5,6]
Output: Node 4 from this list (Serialization: [4,5,6])
Since the list has two middle nodes with values 3 and 4, we return the second one.

2. 풀이

런너기법 를 이용한 풀이

• 워커 러너 테크닉
• walker : 한번에 한칸씩
• runner : 한번에 두칸씩
• runner가 끝나면 walker는 중간에 위치

3. 코드

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode middleNode(ListNode head) {
        ListNode runner = head;

        while (runner != null && runner.next != null) {
            runner = runner.next.next;
            head = head.next;
        }

        return head;
    }
}

• 결과 :

Time Submitted	Status	Runtime	Memory	Language
05/03/2021	Accepted	0 ms	36.6 MB	java

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References

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