Leetcode shortlist sort

Sort by linked list: algorithm-merge sort public class sort {Private Static class listnode {int val; listnode next; listnode (int x) {val = x; next = NULL ;}} private listnode mergelist (listnode head1, listnode head2) {If (head1 = NULL) {return head2;} else if (head2 = NULL) {return head1 ;} listnode head = new listnode (0); listnode TMP = head; while (head1! = NULL & head2! = NULL) {If (head1.val <= head2.val) {head. next = head1; head1 = head1.next;} else {head. next = head2; head2 = head2.next;} head = head. next;} while (head1! = NULL) {head. Next = head1; head1 = head1.next; head = head. Next;} while (head2! = NULL) {head. next = head2; head2 = head2.next; head = head. next;} return TMP. next; // note that a new node is created.} public listnode sortlist (listnode head) {If (Head = NULL | head. next = NULL) {return head;} listnode first = head; listnode after = head; // If (head. next. next = NULL) {First = head. next; head. next = NULL; return mergelist (Head, first);} while (after! = NULL) {If (after. Next! = NULL) {after = after. next. next; first = first. next;} else {break;} listnode TMP = first. next; first. next = NULL; // This is prone to problems. In advance, the backend node is null listnode head1 = sortlist (head); listnode head2 = sortlist (TMP); Return mergelist (head1, head2);} public static void main (string [] ARGs) {response sort = new response sort (); listnode head1 = new listnode (9); head1.next = new listnode (3 ); head1.next. next = new listnode (4); H Ead1.next. next. next = new listnode (1); head1.next. next. next. next = new listnode (5); listnode head = javassort. sortlist (head1); system. out. println ("fuck"); While (Head! = NULL) {system. Out. println (head. Val); Head = head. Next ;}}}