Insertion Sort List

public class Solution {
public ListNode insertionSortList(ListNode head) {
ListNode dummy = new ListNode(-1);

ListNode first = null, last = null;
ListNode cur = head;

while (cur != null) {
ListNode next = cur.next; // save the next node
cur.next = null;

if (first == null || last == null) {
dummy.next = cur;
first = cur;
last = cur;
} else {
if (cur.val <= first.val) {
// insert before the first
dummy.next = cur;
cur.next = first;
first = cur;
} else if (cur.val >= last.val) {
// insert after last
last.next = cur;
last = cur;
} else {
// find the insert place
ListNode node = first;
while (node.next != null) {
if (node.next.val > cur.val) {
break;
}
node = node.next;
}
ListNode tmp = node.next;
node.next = cur;
cur.next = tmp;
}
}

cur = next;
}

return first;
}
}