创建一个 for 循环以将先前的值加倍

Question

我目前正在学习 Java，我有一个作业要求我编写一个 for 循环。我需要创建一个允许用户输入的小程序，然后使用 for 循环放置一条消息，告诉用户他们的信息。我需要 for 循环来允许，总结用户放置的天数和他们每天的粮食，我还需要每天获得双倍的粮食。

示例：

第 1 天你得到 1 粒米，总共 1 粒

第 2 天你得到 2 粒米，总共 3 粒米

第 3 天你得到 4 粒米，总共 7 粒米

第 4 天你得到 8 粒米，总共 15 粒

第 X 天，您获得了 X 粒米，共计 Y 粒

我不太确定如何设置我的 for 循环来执行此操作。这是我目前所拥有的。

    public static void GrainCounter()
{
    Scanner s = new Scanner(System.in);
    System.out.println("How many days worth of grain do you have?");
    int days = s.nextInt();
    int sum = 0;

    for (int i = 0; i <= days; i++)
    {
     sum = sum + i;
    }
    System.out.print("Day " + days + " you got " + sum + " grains of rice");
}

Answer 1

其实公式是，

Day X you get 2**X grains of rice for a total of Y grains

你的 sum 应该从 1 开始，你应该把你的 print 放在循环中（你还想打印 i 一天）。像，

System.out.println("Day 1 you get 1 grain of rice for a total of 1 grain");
int sum = 1;
for (int i = 1; i <= days; i++)
{
 sum += Math.pow(2, i);
 System.out.println("Day " + (i + 1) + " you got " + (int)Math.pow(2,i) + 
     " grains of rice for a total of " + sum + " grains");
}

您也可以将 println 写成

System.out.printf("Day %d you got %d grains of rice for a total of %d grains%n",
        i + 1, (int) Math.pow(2, i), sum);

Answer 2

你所要做的就是用 1 初始化 rice 并在 for 循环中继续将它添加到自身，直到你的循环迭代器 int i 到达天数 - 1（因为你用 1 初始化，所以没有额外的迭代）

public static int doubleDays(int days) {
        int rice = 1;
        for (int i = 0; i < days - 1; i++) {
            rice += rice;
        }
        return rice;
    }

Answer 3

试试这个：

import java.util.Scanner;
public class GrainCounter{
  public static void main(String[] agrs){
      Scanner in = new Scanner(System.in);
      System.out.println("How Many Days Worth Of Grain Do You Have?");
      int days = in.nextInt();
      int sum =1, dailySum=1;
      System.out.println("Day 1 you get 1 grain of rice for a total of 1 grain");
      for (int i =1; i <days; i++){
          dailySum*=2;
          sum +=dailySum;
          System.out.print("Day "+  (i+1) +  " you get "  + dailySum   
                                                + " grain of rice for a total of " 
                                                +  sum + " grain\n");  
     }
  }
}

结果将持续 10 天：

How Many Days Worth Of Grain Do You Have?
10
Day 1 you get 1 grain of rice for a total of 1 grain
Day 2 you get 2 grain of rice for a total of 3 grain
Day 3 you get 4 grain of rice for a total of 7 grain
Day 4 you get 8 grain of rice for a total of 15 grain
Day 5 you get 16 grain of rice for a total of 31 grain
Day 6 you get 32 grain of rice for a total of 63 grain
Day 7 you get 64 grain of rice for a total of 127 grain
Day 8 you get 128 grain of rice for a total of 255 grain
Day 9 you get 256 grain of rice for a total of 511 grain
Day 10 you get 512 grain of rice for a total of 1023 grain

Answer 4

问题是你的代码试图使用天作为变量，但实际上你的变量实际上是前几天的收益。

public static void GrainCounter(){
    Scanner s = new Scanner(System.in);
    System.out.println("How many days worth of grain do you have?");
    int days = s.nextInt();
    int sum = 1;
    previousDay = 1;
    for (int i = 2; i <= days; i++){
        sum += previousDay*2;
        previousDay = previousDay*2;
    }
    System.out.print("Day " + days + " you got " + sum + " grains of rice");
}

创建一个 for 循环以将先前的值加倍

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bluej