LeetCode----- 86.Partition List

Given a linked list and a value x, partition it such that all nodes less than x come before nodes greater than or equal to x.

You should preserve the original relative order of the nodes in each of the two partitions.

For example,
Given 1->4->3->2->5->2 and x = 3,
return 1->2->2->4->3->5.

给定一个链表和一个值x，对它进行分区，使得小于x的所有节点都在大于或等于x的节点之前。您应该保留两个分区中的每一个节点的原始相对顺序。

思路：构造两个新的链表less,more，将小于x值的节点依次插入到less链表，将大于x值的节点依次到more链表。最后more链表的最后一个节点指向null，并且将more链表插入到less链表的后面。

代码如下:

public class PartitionList {public static ListNode partition(ListNode head, int x) {if(head == null || head.next == null ) {return head;}ListNode less = new ListNode(0);ListNode more = new ListNode(0);ListNode node = head,pre = less,front = more;while(node != null) {if(node.val < x) {pre.next= node;pre = pre.next;}else {front.next = node;front = front.next;}node = node.next;}front.next = null;pre.next = more.next;return less.next;}public static void main(String[] args) {ListNode l10 = new ListNode(1);ListNode l11 = new ListNode(2);ListNode l12 = new ListNode(3);ListNode l13 = new ListNode(2);ListNode l14 = new ListNode(5);ListNode l15 = new ListNode(2);l10.next = l11;l11.next = l12;l12.next = l13;l13.next = l14;l14.next = l15;l15.next = null;ListNode node = partition(l10,3);while(node != null) {if(node.next == null) {System.out.println(node.val);}else{System.out.print(node.val +"->");}node = node.next;}}}