递归方法中的逻辑错误

Question

我试图编写一个使用递归方法的程序来计算在投入相同数量的钱（由用户输入）时投入总共1000万美元的目标需要多少个月每月增加2％的利息。问题是该方法太早返回计数器，所以我的“月”输出不准确。我的猜测是我最后的else语句是错误的或我的柜台放置不当

继承人我的代码

import java.util.Scanner; 
    public class MoneyMakerRecursion { 
     public static int counter = 0; 
     public static void main(String[] args) { 
      //Variables declared 
      Scanner userInput = new Scanner(System.in); 
      double investment; 
      //User is prompted for input 
      System.out.println("Enter your monthly investment: "); 
      investment = userInput.nextInt(); 
      //Method is called 
      Sum(investment); 
      //Results from recursive method output 
      System.out.println("It should take " + counter + " month(s) to reach your goal of $10,000,000"); 
     } 
     //recursive Method 
     public static double Sum(double investment) { 
      counter++; 
      double total = (investment * 0.02) + investment; 
      if(total >= 10000000) {return counter;} 
      else {return Sum(investment+total);} 
     } 
    } 

Answer 1

你错过了重要的一点是你每月的投资是在所有个月相同。因此它应该是静态变量。

第二点你加入的投资总量是该方法的局部变量。这不是一个月的实际投资。它的值传递给每个月会发生变化的函数（请考虑您的代码）

请参阅下面的工作代码。

import java.util.Scanner; 
    public class MoneyMakerRecursion { 
     public static int counter = 0; 
     public static double investment = 0; 
     public static void main(String[] args) { 
      //Variables declared 
      Scanner userInput = new Scanner(System.in); 
      //User is prompted for input 
      System.out.println("Enter your monthly investment: "); 
      investment = userInput.nextInt(); 
      //Method is called 
      Sum(investment); 
      //Results from recursive method output 
      System.out.println("It should take " + counter + " month(s) to reach your goal of $10,000,000"); 
     } 
     //recursive Method 
     public static double Sum(double totalInvestment) { 
      counter++; 
      double total = (totalInvestment* 0.02) + totalInvestment; 
      if(total >= 10000000) {return counter;} 
      else {return Sum(total+investment);} 
     } 
    } 

结果

Enter your monthly investment: 
100000 
It should take 55 month(s) to reach your goal of $10,000,000 

这里是快照：这里的兴趣每年进行审议，因此将0.02月息每年利息就变成0.24