Question

java计算运算式1+1*2+1*2*3+1*2*3*4+……+1*2*3*4*……*20的结果并输出.

计算运算式1+1*2+1*2*3+1*2*3*4+……+1*2*3*4*……*20的结果并输出.

Answer 1

class Compute {
public Compute() { } public static void main(String[] args) {
long sum =1;
long a=1;
for (int i = 2; i <= 20; i++) {
a*=i;
sum+=a;
}
System.out.println(sum);
}
}输出结果如下：2561327494111820313

Answer 2

public class t{
public static void main(String []args){
int i,j,sum = 0,t = 0;
for(i = 1;i <= 20;i++) { t = 1; for(j = 1;j <= i;j++) { t *= j; } sum += t; } System.out.println(sum);
}
}

Answer 3

long sum=1;//求和变量
long temp=1;//临时变量 计算n1*n2*n..
for(long i=1;i<=20;i++){
for(long j=1;j<i+1;j++){
temp*=j;
}
sum+=temp;
temp=1;
}
System.out.println(sum);

Answer 4

import java.math.*;public class JiShuang{ public static void main(String args[]) { BigInter sum=new BigInteger("0"), xiang=new BigInteger("1"), ONE=new BigInteger("1"), i=ONE, m=new BigInteger("20"); while(i.compareTo(m)<=0) { sum=sum.add(xiang); i=i.add(ONE); xiang=xiang.ultiply(i); } System.out.println(sum); } }