public static ListNode lineUp (ListNode head) { if (head == null || head.next==null)return head; // write code here ListNode node = head.next; ListNode jishu = head.next; int flag = 2; StringBuilder s = new StringBuilder(); while (node != null){ if(flag % 2 == 1){ jishu.val = node.val; jishu = jishu.next; } else { s.append(node.val).append(" "); } node = node.next; flag++; } String[] strings = s.toString().split(" "); for (String string : strings) { jishu.val = Integer.valueOf(string); jishu = jishu.next; } return head; } 这是我第一题ac代码