【王道JAVA】【程序 21 求阶乘】

题目：求 1+2!+3!+...+20!的和。

public class WangDao {
	public static void main(String[] args){
		int n = 20;
		long sum = 0;
		
		for (int i = 1; i <= n; i++) {
			sum += func(i);
		}
		System.out.println("The factorial from 1 to 20 is " + sum);
	}
	
	public static long func(int n) {	// 返回值一定得是long，因为20!很大。
		int factorial = 1;
		
		for (int i = 1; i <= n; i++) {
			factorial *= i;
		}
		
		return factorial;
	}
}