LeetCode in Net
86. Partition List
Medium
Given the head of 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.
Example 1:
Input: head = [1,4,3,2,5,2], x = 3
Output: [1,2,2,4,3,5]
Example 2:
Input: head = [2,1], x = 2
Output: [1,2]
Constraints:
- The number of nodes in the list is in the range
[0, 200]. -100 <= Node.val <= 100-200 <= x <= 200
Solution
using LeetCodeNet.Com_github_leetcode;
/**
* Definition for singly-linked list.
* public class ListNode {
* public int val;
* public ListNode next;
* public ListNode(int val=0, ListNode next=null) {
* this.val = val;
* this.next = next;
* }
* }
*/
public class Solution {
public ListNode Partition(ListNode head, int x) {
ListNode beforeHead = new ListNode(0);
ListNode afterHead = new ListNode(0);
ListNode before = beforeHead;
ListNode after = afterHead;
while (head != null) {
if (head.val < x) {
before.next = head;
before = before.next;
} else {
after.next = head;
after = after.next;
}
head = head.next;
}
after.next = null;
before.next = afterHead.next;
return beforeHead.next;
}
}