83 Remove Duplicates from Sorted List

循环过一遍， 如果和上一个元素相同，那么忽略它，不同，则添加到新的链表里面。

可以多使用一个循环减少多余的空间开销。

Python

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def deleteDuplicates(self, head):
        """
        :type head: ListNode
        :rtype: ListNode
        """
        if head is None:
            return None
        new_head = ListNode(head.val)
        cur = new_head
        p = head.next
        while p:
            if p.val != cur.val:
                cur.next = ListNode(p.val)
                cur = cur.next
            p = p.next
        return new_head

Java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode deleteDuplicates(ListNode head) {
        ListNode ret = new ListNode(-1);
        ret.next = head;
        while(head != null){
            while(head.next != null && head.next.val == head.val){
                head.next = head.next.next;
            }
            head = head.next;
        }
        return ret.next;
    }
}