Given a linked list and a specific value x, please separate the linked list so that all nodes less than x appear before nodes greater than or equal to x.
You should keep the initial relative position of each node in the two partitions.
Example:
Input: head = 1->4->3->2->5->2, x = 3
Output: 1->2->2->4->3->5
Source: LeetCode
Link: https://leetcode-cn.com/problems/partition-list
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/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
//直观来说我们只需维护两个链表 \textit{small}small 和 \textit{large}large 即可,\textit{small}small 链表按顺序存储所有小于 xx 的节点,\textit{large}large 链表按顺序存储所有大于等于 xx 的节点。遍历完原链表后,我们只要将 \textit{small}small 链表尾节点指向 \textit{large}large 链表的头节点即能完成对链表的分隔。
public ListNode partition(ListNode head, int x) {
ListNode small = new ListNode(0);
ListNode smallHead = small;
ListNode large = new ListNode(0);
ListNode largeHead = large;
while(head!=null)
{
if(head.val<x){
small.next = head;
small = small.next;
}else{
large.next = head;
large = large.next;
}
head = head.next;
}
large.next = null;
small.next = largeHead.next;
return smallHead.next;
}
}