HDU—OJ 、2011

import java.util.Arrays;
import java.util.Scanner;

public class Polynomial_Summation {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while (scanner.hasNext()) {
            //几个数据
            String m = scanner.nextLine();          
            //测试的实例
            String n = scanner.nextLine();          
            String[] strs = n.split(" ");

            int[] instance = new int[100];
            for (int i = 0; i < strs.length; i++) {
                instance[i] = Integer.parseInt(strs[i]);    
                double sum = 0.0;
                for (int j = 1; j <= instance[i]; j++) {

                    if (j%2 == 0) {
                        sum = sum - (double)1/j;
                    }else {
                        sum = sum + (double)1/j;
                    }
                }

                System.out.println(String.format("%.2f", sum));

            }

        }
    }
}

注意：两个整数相除自动舍去小数。