java如何用while循环求2的幂和

Question

我需要计算2^0+2^1+2^2+...+2^n的和，其中n是用户输入的数字。主要的问题是，我不知道如何使用while循环来总结2^n的不同结果

以下是我尝试过的：

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());

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

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

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

Answer 1

你唯一要做的就是：

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);

    }
}

在这里，{a1}解释了数学表达式

Answer 2

下面是一个带有注释的解决方案来解释逻辑。而循环需要某种变量来控制迭代次数。当然，这个变量需要在循环中的某个地方进行更新

你可以用数学计算幂和。显然是pow（）函数。使用它不需要导入语句。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 3

你计算幂和，然后完全忽略它，只是打印出2^i的结果。你应该打印出sum，比如：

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

对于样式点，这不会处理负幂，所以需要进行测试

Answer 4

不明白在这种情况下为什么要循环。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loop，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 5

好的，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 6

你的条件句是倒转的，应该是：

while (i <= power)