LeetCode82.java

public class LeetCode82 {
    public ListNode deleteDuplicates(ListNode head) {
        // 特殊情况判断
        if(head == null || head.next == null) return head;
        // 设置虚拟头结点
        ListNode dummyHead = new ListNode(-101);
        dummyHead.next = head;
        //pre指针指向cur1指针的前一个节点
        ListNode pre = dummyHead;
        //cur1指针指向当前节点
        ListNode cur1 = head;
        //cur2指针用来遍历
        ListNode cur2 = head;
        //记录数字出现的次数
        int count = 0;
        //cur2指针用来遍历
        while(cur2 != null){
            //循环找下一个不同的元素
            while(cur2 != null && cur1.val == cur2.val){
                cur2 = cur2.next;
                count++;
            }
            //如果次数为1，则不用删，pre和cur1向后移动一次
            if(count == 1){
                cur1 = cur1.next;
                pre = pre.next;
            }
            //否则讲pre的下一个节点指向cur2，并让cur1指向cur2
            else{
                pre.next = cur2;
                cur1 = cur2;
            }
            //次数还原
            count = 0;
        }
        return dummyHead.next;
    }
    //LeetCode官方解法
    public ListNode deleteDuplicates2(ListNode head) {
        ListNode dummy = new ListNode(-101);
        if (head == null || head.next == null)
            return head;
        dummy.next = head;
        ListNode cur = dummy;
        while (cur.next != null && cur.next.next != null) {
            if (cur.next.val == cur.next.next.val){
                int x = cur.next.val;
                while (cur.next != null && cur.next.val == x){
                    cur.next = cur.next.next;
                }
            }else {
                cur = cur.next;
            }
        }
        return dummy.next;
    }
}