遞歸方法中的邏輯錯誤

Question

我試圖編寫一個使用遞歸方法的程序來計算在投入相同數量的錢（由用戶輸入）時投入總共1000萬美元的目標需要多少個月每月增加2％的利息。問題是該方法太早返回計數器，所以我的「月」輸出不準確。我的猜測是我最後的else語句是錯誤的或我的櫃檯放置不當

繼承人我的代碼

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

你錯過了重要的一點是你每月的投資是在所有個月相同。因此它應該是靜態變量。

第二點你加入的投資總量是該方法的局部變量。這不是一個月的實際投資。它的值傳遞給每個月會發生變化的函數（請考慮您的代碼）

請參閱下面的工作代碼。

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);} 
     } 
    } 

結果

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

這裏是快照：這裏的興趣每年進行審議，因此將0.02月息每年利息就變成0.24