就第二题过了。。。 public static void main(String[] args) { // TODO Auto-generated method stub Scanner in = new Scanner(System.in); int n = in.nextInt(); int w = in.nextInt(); int len = n * 2; double[] a = new double[len]; for (int i = 0; i < len; i++) { a[i] = in.nextDouble(); } Arrays.sort(a); double x = a[n]; double y = a[0]; double result = 0; if(x>=y*2) { result = 3*n*y; }else { result = (x/2.0*n)+x*n; } result = Math.min(result, w); System.out.printf("%.6f\n",result); }