爱奇艺奶牛问题： import java.math.BigInteger; import java.util.Arrays; import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner in = new Scanner(System.in); int n = in.nextInt(); int[] arr = new int[n]; for(int i = 0; i<n; i++){ arr[i] = in.nextInt(); } Arrays.sort(arr); Main solutionWay = new Main (); System.out.println(solutionWay.solution(n,arr)); } public BigInteger solution(int n, int[] arr){ BigInteger num = BigInteger.valueOf(1); final BigInteger mode = BigInteger.valueOf(1000000007L); for(int i = 0; i < arr.length; i++){ if(arr[i] - i > 0){ num = num.multiply( BigInteger.valueOf(arr[i]-i)); } else{ num = BigInteger.valueOf(0); } } return num.mod(mode); } }