Question

我正在开发一个Java 2类的项目，该项目必须显示用户输入的一段时间内有机体的人口增长。我能够使用while循环实现该方法，但很难将其转换为递归方法。

while(day <= totalDays)
{
    if (day == 1){
        System.out.println(organs);
        day++; //day one there is no increase
    }
    else{
        organs = organs + organs*(increase/100); //add % increase of organisms
        System.out.println(organs);
        day++;}
}

到目前为止，这是我对递归方法的尝试失败。

public static double showPopulation(int dayNum, int days, double organisms, 
        double dailyIncrease)
{
    if(dayNum == totalDays)
    {
        return organisms + (organisms*dailyIncrease);
    }
    else
        return showPopulation(dayNum+1, days, organisms, dailyIncrease) + organisms*dailyIncrease;

Answer 1

通过showPopulation(totalDays, organ, dailyIncrease)调用以下函数。在此，我假设totalDays是整个天数，organ是＆＃34; organ＆＃34;的初始值，dailyIncrease是百分比。

public static double showPopulation(int dayNum, double organ, double dailyIncrease) {
    if(dayNum <= 1) {
        return organ;
    } else {
        return (1 + dailyIncrease) * showPopulation(dayNum - 1, organ, dailyIncrease);
    }
}

通常，在使用迭代时，我们通常从基本情况开始。就这个问题而言，它意味着第1天或dayNum == 1。而在应用递归时，我们通常会从程序的最终状态开始考虑问题。在这个问题中，它表示最后一天（totalDays）。

Answer 2

虽然我猜这是家庭作业，但这是它应该如何运作

public static double showPopulation(int dayNum, double organisms, 
        double dailyIncrease)
{
    if(dayNum == 1)
    {
        return organisms + (organisms*dailyIncrease);
    }else{
        return showPopulation(dayNum-1, organisms, dailyIncrease) + organisms*dailyIncrease;
    }
}

我没有运行它，所以要小心进一步的错误。

您忘记了终止条件。它必须总是更接近这个条件，通常是减少直到达到0或类似。

Answer 3

   public int population(int days, int startingOrganisms, double dailyIncrease) {
      if (days <= 1) {
         System.out.print(days + " " + startingOrganisms);
         //no increase, finish condition
         return startingOrganisms;
      } else {
         // we need to find the population of yesterday to know how much organisms exist today
         int populationYesterday = population(days - 1, startingOrganisms, dailyIncrease);
         int populationToday = populationYesterday + (populationYesterday * dailyIncrease / 100);

         System.out.print(days + " " + populationToday);
         return populationToday;
      }
   }

然后只需调用它并打印结果

System.out.println( population(10, 1000, 30.2);

您是否需要在每一步中打印增长？

Answer 4

试试这段代码：

public static double showPopulation(int totalDay,int days, double organisms, 
            double dailyIncrease)  {
        if(days == totalDay) {
            return organisms;
        }
        else{
            organisms+=organisms*dailyIncrease;
            return showPopulation(totalDay,++days, organisms, dailyIncrease);
        }

    }

使用递归方法而不是while循环

4 个答案: