给定一个排序链表,删除所有含有重复数字的节点,只保留原始链表中没有重复出现的数字。
举例:
原链表: 1->2->3->3->4->4->5
删除后: 1->2->5
解法1:
结合删除重复节点和删除指定节点的方式,可以先删除重复节点,并记录下来重复节点的值,然后再删除指定节点的值即可。
public class Code_06 {
public static void main(String[] args) {
Code_06 c = new Code_06();
ListNode n = new ListNode();
ListNode head = n;
for (int i = 1; i <= 5; i++) {
n.next = new ListNode(i);
n = n.next;
if (i % 2 == 0) {
n.next = new ListNode(i);
n = n.next;
}
}
System.out.println(head);
System.out.println(c.deleteDuplicates(head));
}
public ListNode deleteDuplicates(ListNode head) {
ListNode cur = head;
Set<Integer> dupSet = new HashSet<>();
while (cur != null && cur.next != null) {
if (cur.val != cur.next.val) {
cur = cur.next;
} else {
dupSet.add(cur.val);
cur.next = cur.next.next;
}
}
for (Integer val : dupSet) {
head = deleteNode(head, val);
}
return head;
}
private ListNode deleteNode(ListNode head, int val) {
while (head != null) {
if (head.val != val) {
break;
}
head = head.next;
}
ListNode pre = null;
ListNode cur = head;
while (cur != null) {
if (cur.val == val) {
pre.next = cur.next;
} else {
pre = cur;
}
cur = cur.next;
}
return head;
}
}
第一种方式显然不够优雅,换一种思路,通过哑节点+双指针实现
public class Code_06_01 {
public static void main(String[] args) {
Code_06_01 c = new Code_06_01();
ListNode n = new ListNode();
ListNode head = n;
for (int i = 1; i <= 5; i++) {
n.next = new ListNode(i);
n = n.next;
if (i % 2 == 0) {
n.next = new ListNode(i);
n = n.next;
}
}
System.out.println(head);
System.out.println(c.deleteDuplicates(head));
}
/**
* 哑节点+双指针
* <p>
* 构建一个哑节点,让其next指向头位置。
* 再利用双指针,n1,n2,初始都指向head位置,如果n1.next.val==n2.next.val,则让n2向前移动一位,否则n1,n2一起向前移动一位
*
* @param head
* @return
*/
public ListNode deleteDuplicates(ListNode head) {
ListNode dummy = new ListNode();
dummy.next = head;
ListNode n1 = dummy;
ListNode n2 = head;
while (n2 != null && n2.next != null) {
if (n1.next.val != n2.next.val) {
n1 = n1.next;
} else {
//n2一直移动,直到不等于n1为止
while (n2 != null && n2.next != null && n1.next.val == n2.next.val) {
n2 = n2.next;
}
n1.next = n2.next;
}
n2 = n2.next;
}
return dummy.next;
}
}