创建一个for循环以使之前的值翻倍

Question

我目前正在学习Java，我有一个任务，要求我编写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循环将消息告诉用户他们的信息。我需要for循环来允许，总结用户投入的天数，以及他们每天的谷物数量，同时我还需要每天获得两倍的谷物数量。

实施例：

第1天你得到1粒米，总共1个晶粒

日的2你得到2个晶粒大米的总共3粒

3你日大米共计7粒

4日的4粒你得到8粒米，共15粒

X天的你米X谷物的TOT Y晶粒

我不完全确定如何设置我的for循环来做到这一点。这是我到目前为止。

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

的公式实际上是，

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

你sum应该1开始，你应该把你print在循环（也想要打印i为天）。喜欢的东西，

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"); 
} 

你也可以写println作为

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

所有你需要做的是初始化rice与1，只是不断增加它本身在for -loop，直到你的循环迭代int i达到天数-1（因为您初始化为1，所以不需要额外的迭代）

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"); 
    } 
    } 
} 

结果将是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一天作为变量，但实际上您的变量实际上是前几天的获得。

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"); 
}