[LeetCode80]Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,

Given

1->2->3->3->4->4->5

, return

1->2->5

.

Given

1->1->1->2->3

, return

2->3

.

Analysis

The idea is same with the Question 79 Remove Duplicates from Sorted List.

Difference is there needs a safe head and flag to record whether former is duplicate

java

public ListNode deleteDuplicates(ListNode head) {
        if(head == null || head.next == null) return head;
        ListNode newHead = new ListNode(-1);
        newHead.next = head;
        ListNode p1 = newHead;
        ListNode p2 = head;
        while(p2!=null){
        	boolean dup = false;
        	while(p2.next!=null && p2.val == p2.next.val){
        		dup = true;
        		p2 = p2.next;
        	}
        	if(dup){
        		p2 = p2.next;
        		continue;
        	}
        	p1.next = p2;
        	p1 = p1.next;
        	p2 = p2.next;
        }
        p1.next = p2;
        return newHead.next;
    }

c++

ListNode *deleteDuplicates(ListNode *head) {
        if(head == NULL || head->next == NULL){
            return head;
        }
        ListNode *p = new ListNode(-1);
        p->next = head;
        ListNode *cur = p, *pre = head;
        while(pre != NULL){
            bool isDupli = false;
            while(pre->next != NULL && pre->val == pre->next->val){
                isDupli = true;
                pre = pre->next;
            }
            if(isDupli){
                pre = pre->next;
                continue;
             
            }
            cur->next = pre;
            cur = cur->next;
            pre = pre->next;
            
        }
        cur->next = pre;
        return p->next;
    }

用JUnit 单元测试

@Test
	public void test() {
		//new linked list
		ListNode head = new ListNode(1);
		ListNode l1 = new ListNode(1);
		ListNode l2 = new ListNode(1);
		ListNode l3 = new ListNode(2);
		ListNode l4 = new ListNode(3);
		//link nodes
		head.next = l1;
		l1.next = l2;
		l2.next = l3;
		l3.next = l4;
		l4.next = null;
		//pass link list to method
		RemoveDuplicateFromSortedList reList = new RemoveDuplicateFromSortedList();
		reList.deleteDuplicates2(head);
	}