leetcode148. 排序链表(java)

第一次做这个

学习题解用的优先队列（小根堆）很巧妙

class Solution {
    public ListNode sortList(ListNode head) {
        if(head == null) return null;
        PriorityQueue pq =  new PriorityQueue<>();
        ListNode a = head;
        while(a != null){
            pq.offer(a.val);
            a = a.next;
        }
        ListNode b = new ListNode(0);
        ListNode ans = b;
        while(pq.size() > 0){
            b.val  = pq.poll();
            if(pq.size() > 0){
                ListNode tmp = new ListNode(0);
                b.next = tmp;
            }
            b = b.next;
        }
        return ans;
    }
}