勉强这样过了 public static void nums(int n) { if(n<8712) { System.out.println(0); return ; } if (n>=8712 && n<=10000) { System.out.println(1); System.out.println("2178 8712"); return ; } int max = n/4; LinkedList<String> res = new LinkedList<String>(); res.add("2178 8712"); for(int i=10000; i<max; i++) { int flag = i*4; String a = String.valueOf(i); String b = String.valueOf(flag); if(isEq(a, b)) { res.add(a+" "+b); } } System.out.println(res.size()); for (String s : res) { System.out.println(s); } return ; } public static void main(String[] args) { Scanner sc = new Scanner(System.in); int n = sc.nextInt(); nums(n); } public static boolean isEq(String a, String b) { if(a.length() != b.length()) { return false;} for(int i=0; i<a.length(); i++) { if(a.charAt(i) != b.charAt(a.length()-1-i)) { return false; } } return true; }