Thursday, February 4, 2016

Remove Duplicates from Unsorted List

Remove Duplicates from Unsorted List

Write code to remove duplicates from an unsorted linked list.

Example
Given 1->3->2->1->4.
Return 1->3->2->4
Challenge

(hard) How would you solve this problem if a temporary buffer is not allowed? In this case, you don't need to keep the order of nodes.


 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
/**
 * Definition for ListNode
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param head: The first node of linked list.
     * @return: head node
     */
    public ListNode removeDuplicates(ListNode head) { 
        // Write your code here
        HashSet<Integer> hash = new HashSet<Integer>();
        
        ListNode cur = head;
        if (head == null) {
            return head;
        }
        hash.add(cur.val);
        while (cur.next != null) {
            if (hash.contains(cur.next.val)) {
                cur.next = cur.next.next;
            }
            else {
                hash.add(cur.next.val);
                cur = cur.next;
            }
        }
        return head;
    }  
}
Posted by at