[leetcode] Partition List

Use two dummy list standing for less than and greater or equal to

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

public class Solution { public ListNode partition(ListNode head, int x) { ListNode less = new ListNode(-1); ListNode greatEq = new ListNode(-1); ListNode currentLess = less, currentGeq = greatEq; while (head != null){ ListNode next = head.next; head.next = null; if (head.val < x){ currentLess.next = head; currentLess = head; }else{ currentGeq.next = head; currentGeq = head; } head = next; } if (currentLess == less){ return greatEq.next; } currentLess.next = greatEq.next; return less.next; } }