LeetCode Partition List

Description:

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.

Solution:

还是两个指针，一个记录小于x，一个记录大于等于x。

import java.util.*;

public class Solution {
	public ListNode partition(ListNode head, int x) {
		ListNode smallerHead = null, biggerHead = null;
		ListNode smallerTot = smallerHead, biggerTot = biggerHead;
		ListNode temp = head, neo, next;

		while (temp != null) {
			next = temp.next;
			temp.next = null;
			if (temp.val < x) {
				if (smallerHead == null) {
					smallerHead = temp;
					smallerTot = temp;
				} else {
					smallerTot.next = temp;
					smallerTot = smallerTot.next;
				}
			} else {
				if (biggerHead == null) {
					biggerHead = temp;
					biggerTot = temp;
				} else {
					biggerTot.next = temp;
					biggerTot = biggerTot.next;
				}
			}
			temp = next;
		}

		if (smallerHead == null)
			return biggerHead;
		else {
			smallerTot.next = biggerHead;
			return smallerHead;
		}
	}
}