题解 | #N的阶乘#

import java.util.Scanner;
import java.math.BigInteger;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNextInt()) {
            int n = in.nextInt();
            // BigInteger res = BigInteger.valueOf(1);
            BigInteger res = new BigInteger("1");
            for(int i = 1;i<=n;i++){
                // res.multiply(BigInteger.valueOf(i));
                res=res.multiply(new BigInteger(""+i));
            }
            System.out.println(res);
        }


    }
}

multiply调用完后要赋值回去。。。我还以为是valueOf的原因一直调试