Question

用JAVA编写一个求1!+2!+3!+.....+10!的程序

Answer 1

public class Calculate {

/**
* 计算一个数的阶乘
* @param number
* @return
*/
public static int factorial(int number){
int result = 1;
if(number <=0){
return result;
}else{
for(int i=number;i>=1;i--){
result *=i;
}
}
return result;
}

/**
* 计算小于等于输入数字的所有数字的阶乘求和
* @param number
* @return
*/
public static int calculate(int number){
int result = 0;
for(int i=1;i<=number;i++){
result += Calculate.factorial(i);
}
return result;
}

public static void main(String[] args) {
System.out.println(Calculate.calculate(1));
System.out.println(Calculate.calculate(2));
System.out.println(Calculate.calculate(3));
System.out.println(Calculate.calculate(4));
System.out.println(Calculate.calculate(10));
}
}

//运行结果：

1
3
9
33
4037913

Answer 2

public class aaaa{
public static void(String args[]){
int i=1,j=1;
int sum=0;
for(;i<=10;i++){
j=j*i;sum=sum+j;}
System.out.println(sum);
}
}

Answer 3

public class Cal
{

public static void main(String arg[])
{
private int lastResult=1;
private int sum=0;
for(int c=1;c<=10;c++)
{
lastResult=lastResult*c;
sum=sum+lastResult;
}
System.out.println(sum);
}
}
这应该是最快的算法了,利用n!=n((n-1)!).