83 Remove Duplicates from Sorted List

83. Remove Duplicates from Sorted List

1. Question

Given a sorted linked list, delete all duplicates such that each element appear onlyonce.

For example, Given1->1->2, return1->2. Given1->1->2->3->3, return1->2->3.

2. Implementation

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        if (head == null) {
            return head;
        }

        ListNode preNode = head, curNode = head.next;
        while (curNode != null) {
            if (preNode.val == curNode.val) {
                preNode.next = curNode.next;
            }
            else {
                preNode = preNode.next;
            }
            curNode = curNode.next;
        }
        return head;
    }
}

3. Time & Space Complexity

时间复杂度O(n), 空间复杂度O(1)