1066 problem: the fall of 2004, Zhejiang Province Computer Rank Examination two C programming problem (2)

Title Description

Enter a positive number x and a positive integer value of n, the following formula is required. Requires the definition of two function calls: fact (n) calculated n factorial; mypow (x, n) n-th power of x (i.e., xn), two types of function return value is double.

      x - x2/2! + x3/3! + ... + (-1)n-1xn/n!

 

× outputs a 4 decimal places.

 

Entry

x n

Export

Sequence sum

Sample input

2.0 3

Sample Output

1.3333

import java.util.Scanner;

public class Main{
public static void main(String args[]){
　　Scanner in = new Scanner(System.in);
　　double x = in.nextDouble();
　　int n = in.nextInt();
　　double y=0.0;
　　double sum=0.0;
　　for(int i=1;i<=n;i++){
　　　　y=Math.pow(-1, i-1)*mypow(x,i)/fact(i);
　　　　sum+=y;
}
　　System.out.printf("%.4f", sum);


}
　　public static double fact(int n){
　　　　double a=1;
　　　　for(int i=1;i<=n;i++){
　　　　　　a=a*i;
　　}
　　　　return a;
}
　　public static double mypow(double x, int n){
　　return Math.pow(x, n);
}
}