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PartitionList.java
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PartitionList.java
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package Leetcode;
/**
* @author kalpak
*
* 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 tree is in the range [0, 200].
* -100 <= Node.val <= 100
* -200 <= x <= 200
*
*/
public class PartitionList {
public static ListNode partition(ListNode head, int x) {
ListNode smallerThanXHead = new ListNode(0);
ListNode smallerThanXdummy = smallerThanXHead;
ListNode greaterThanXHead = new ListNode(0);
ListNode greaterThanXdummy = greaterThanXHead;
while(head != null) {
if(head.val < x) {
smallerThanXdummy.next = head;
smallerThanXdummy = smallerThanXdummy.next;
} else {
greaterThanXdummy.next = head;
greaterThanXdummy = greaterThanXdummy.next;
}
head = head.next;
}
greaterThanXdummy.next = null; // Terminate the list
smallerThanXdummy.next = greaterThanXHead.next; // Connect the smaller list to the greater list
return smallerThanXHead.next;
}
public static void printList(ListNode head) {
while(head != null) {
System.out.print(head.val + " ");
head = head.next;
}
System.out.println();
}
public static void main(String[] args) {
ListNode head = new ListNode(1);
head.next = new ListNode(4);
head.next.next = new ListNode(3);
head.next.next.next = new ListNode(2);
head.next.next.next.next = new ListNode(5);
head.next.next.next.next.next = new ListNode(2);
partition(head, 3);
printList(head);
}
}