import java.util.Scanner;
class Recursion{
public static void main(String argv[]){
System.out.println("chose the method to implement N! 1:recursion 2:not the recursion");
int n=0;
Scanner scanner = new Scanner(System.in);
n = scanner.nextInt();
if(n==1){
System.out.println("input the n value: ");
n = scanner.nextInt();
System.out.println("the n! value are " + recursion(n));
}else if(n==2){
System.out.println("input the n value: ");
n = scanner.nextInt();
System.out.println("the n! value are " + noRecursion(n));
}
}
/*the recursion to implement the n!*/
public static long recursion(int n){
long res = 1;
if(n<=0){
res = 0;
return res;
}else if(n==1){
res = 1;
}else{
res = recursion(n-1)*n;
}
return res;
}
/*the simple method to implement the n!*/
public static long noRecursion(int n){
long res = 1;
if(n<=0){
res = 0;
return res;
}else if(n==1){
res = 1;
}else{
for(int i=1; i<=n; i++){
res *= i;
}
}
return res;
}
