Question

我需要计算select p.*, ( select count(distinct s.song_id) from playlist_songs ps join songs s on s.song_id = ps.song_id join artists art on s.artist_id = art.artist_id where p.playlist_id = ps.playlist_id ) number_of_songs from playlist p where number_of_songs > 1;的总和，其中2^0+2^1+2^2+...+2^n是用户输入的数字。主要问题是我不知道如何使用while循环来总结n的不同结果。

以下是我尝试的内容：

2^n

Answer 1

只有你必须做的是：

import java.util.Scanner;

public class SumOfThePowers {

    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);

        System.out.println("Type a power: ");
        int power = Integer.parseInt(reader.nextLine());

        double sum = Math.pow(2,power+ 1 ) - 1;
        System.out.println("The sum is: " + sum);

    }
}

在此link解释数学表达式

Answer 2

你的条件是倒退的，应该是：

while (i <= power)

Answer 3

你计算权力之和，然后完全忽略它，只打印出2 ^ i的结果。你应该打印出总和，如：

while (i <= power) {
   sum += Math.pow(number, i);
   i++;
}
System.out.println("The sum is: " + sum);

对于样式点，这不会处理负面的力量，所以你需要测试它。

Answer 4

一切都很好，只是一些变化。将零件代码更改为

        System.out.println("Type a power: ");
        int power = Integer.parseInt(reader.nextLine());
        int number = 2;
        int i = 0;
        double sum = 0;
/*Remove this -------->  while(power <= i) {*/
        while (i <= power) {//it should be this
/*Remove this ------->   Math.pow(number, i);*/
            sum = sum + Math.pow(number, i);
            i = i + 1;
        }
        System.out.println("The sum is: " + sum);

Answer 5

不明白你为什么要在这种情况下循环。你可以这样做：

System.out.println("The sum is: "+(Math.pow(2, power+1)-1 ));

但如果你真的想使用循环试试这个：

        Scanner reader = new Scanner(System.in);

        System.out.println("Type a power: ");
        int power = Integer.parseInt(reader.nextLine());

        int number = 2; 
        int i = 0;
        double sum = 0;

        while(i<=power) {
            sum = sum + Math.pow(number, i);
            i = i + 1;
        }

        int result = (int)Math.pow(number, i);
        System.out.println("The sum is: " + sum);

Answer 6

这是一个解释逻辑的解决方案。 while循环需要某种变量来控制迭代次数。该变量当然需要在内部循环中更新。

显然，您可以使用Math.pow（）函数计算幂的总和。使用它不需要import语句。我希望这有帮助。祝你好运。

    /* Scanner and variable to get and hold user input */
    Scanner scan = new Scanner( System.in );
    int userInput = 0;

    /* Variable to hold the sum, initialized to 0.0 */
    double sum = 0.0;

    /* Prompt the user, and obtain the reply */
    System.out.print( "Enter the exponent: ");
    userInput = scan.nextInt();

    /* The while loop and it's initialized counter */
    int counter = 0;    
    while( counter <= userInput ){

        /* Add each power to sum using Math.pow() */
        sum = sum + Math.pow( 2, counter );

        /* Watch the output as the loop runs */
        System.out.println( "Sum: " + sum );

        counter++;  // Increment counter, so the loop exits properly

    } // End while loop

Answer 7

public class SumofSquare {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        String c = "123";
        char d[] = c.toCharArray();
        int a[] = new int[d.length + 1];

        for (int i = 0; i < d.length; i++)
            a[i] = d[i] - 48;

        int r = 0;

        for (int i = 0; i < c.length(); i++)
            r = r + (int) Math.pow(a[i], a[i + 1]);

        System.out.println(r);
    }
}

Answer 8

import java.util.Scanner;

public class SumOfThePowers {

    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
         System.out.println("Type a number:");
        int power=Integer.parseInt(reader.nextLine());
        int number=2;
        int i=0;
        int result=0;
        while (power>=i) {
            result += (int)Math.pow(number, i);
            i++;
        }
        System.out.println("The result is "+result);
    }
}

Answer 9

import java.util.Scanner;

public class SumOfThePowers {
public static void main(String[] args) {
    Scanner reader = new Scanner(System.in);
    System.out.println("Type a number:");
    double power=Double.parseDouble(reader.nextLine());
    int number=2;
    int i=0;
    double sum=0;
    while (power>=i) {
        sum=sum+Math.pow(number, i);
        i++;
    }
    System.out.println("The sum is "+sum);

}

如何用while循环加总2的幂

9 个答案: