[JAVA] 83. Remove Duplicates from Sorted List

목차

문제

Given the head of a sorted linked list, delete all duplicates such that each element appears only once. Return the linked list sorted as well.

 

Example 1:

Input: head = [1,1,2]
Output: [1,2]

Example 2:

Input: head = [1,1,2,3,3]
Output: [1,2,3]

 

Constraints:

• The number of nodes in the list is in the range [0, 300].
• -100 <= Node.val <= 100
• The list is guaranteed to be sorted in ascending order.

---

풀이

JAVA 

재귀함수 사용

/**
 * 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; }
 * }
 */

public ListNode deleteDuplicates(ListNode head) {
        if(head == null || head.next == null) {
        	return head;
        }
        
        head.next = deleteDuplicates(head.next);
        
        return head.val == head.next.val ? head.next : head;
}

재귀 사용하지 않은 풀이 (완벽한 풀이 아니므로 참고만.)

/**
 * 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; }
 * }
 */

private ListNode deleteDuplicates(ListNode head) {
        ListNode current = head;
        
        while (current != null && current.next != null) {
            if (current.val == current.next.val) {
                current.next = current.next.next;
            } 
            else {
                current = current.next;
            }
        }
        
        return head;
}