Remove Duplicates from Sorted List II
描述
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.
分析
无
递归版
// Remove Duplicates from Sorted List II
// 递归版，时间复杂度O(n)，空间复杂度O(1)
class Solution {
public ListNode deleteDuplicates(ListNode head) {
if (head ==null || head.next == null) return head;
ListNode p = head.next;
if (head.val == p.val) {
while (p != null && head.val == p.val) {
p = p.next;
}
return deleteDuplicates(p);
} else {
head.next = deleteDuplicates(head.next);
return head;
}
}
};迭代版
// Remove Duplicates from Sorted List II
// 迭代版，时间复杂度O(n)，空间复杂度O(1)
public class Solution {
public ListNode deleteDuplicates(ListNode head) {
if (head == null) return head;
ListNode dummy = new ListNode(Integer.MAX_VALUE); // 头结点
dummy.next = head;
ListNode prev = dummy, cur = head;
while (cur != null) {
boolean duplicated = false;
while (cur.next != null && cur.val == cur.next.val) {
duplicated = true;
cur = cur.next;
}
if (duplicated) { // 删除重复的最后一个元素
cur = cur.next;
continue;
}
prev.next = cur;
prev = prev.next;
cur = cur.next;
}
prev.next = cur;
return dummy.next;
}
}