[LeetCode]Merge Two Sorted Lists

双指针，不多说，代码如下：

	/**
	* Definition for singly-linked list.
	* public class ListNode {
	* int val;
	* ListNode next;
	* ListNode(int x) {
	* val = x;
	* next = null;
	* }
	* }
	*/
	public class Solution {
	public ListNode deleteDuplicates(ListNode head) {
	if (head == null)
	return head;
	ListNode sentinel = new ListNode(0);
	sentinel.next = head;
	ListNode ptr1 = sentinel, ptr2 = head;
	int count = 0, base = head.val;
	while (true) {
	while (ptr2 != null && ptr2.val == base) {
	count++;
	ptr2 = ptr2.next;
	}
	if (count == 1)
	ptr1 = ptr1.next;
	ptr1.next = ptr2;
	if (ptr2 == null) {
	if (count > 1)
	ptr1.next = null;
	break;
	}
	count = 0;
	base = ptr2.val;
	}
	return sentinel.next;
	}
	}

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