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I am trying to make a Python program to solve the following problem:

A large number of ants live on the island of Eden and reproduce at a rate of 40% per month. There is also an anteater on the island that eats 7,000 ants at the end of each month (or all the ants there are if the ant population at that time is less than 7,000).

When the population of ants on the island exceeds the maximum of 28,000, feeding problems begin to occur, which reduces the growth rate to 31% per month.

Write the function count_ants that receives as parameters the number of ants that are at a given time on the island and a number of months. The function must calculate how many ants there will be on the island after that number of months.

Assume that population sampling is done only at the end of the month and that the anteater only eats at the end of the month.

This is my code:

def count_ants(current_ants, months):
     growth_rate = 0.4 # Monthly growth rate of 40%
     reduced_growth_rate = 0.31 # Reduced monthly growth rate of 31%
     maximum_capacity = 28000 # Maximum capacity of the island
     anteater = 7000 # Number of ants the anteater eats at the end of each month

     for _ in range(months):
         if current_ants > 0:
             if current_ants <= maximum_capacity:
                 current_ants += int(current_ants * growth_rate)
                 current_ants -= min(current_ants, anteater)
             else:
                 current_ants += int(current_ants * reduced_growth_rate)
                 current_ants -= min(current_ants, anteater)

     return current_ants

My code works for the following cases:

  • Correctly calculate cases with more than 7,000 ants at the end of the month
  • Correctly calculates cases with more than 7000 ants in several months
  • Correctly calculates cases with less than 7000 ants and one month
  • Correctly calculates cases with less than 7000 ants and two months
  • Correctly calculate cases without ants
  • Correctly calculate cases with more than 28,000 ants at the end of the month

But it seems to fail in this one :

NO Correctly calculates cases with more than 28,000 ants in several months Your program failed when these inputs were used: initial_quantity: 28000 months: 4 Your program responded: 44205

I want to know why this particular test case failed. Thanks!

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  • 2
    Just a note, since both times you are subtracting the anteater eats count the same way you can take that out of the if blocks and write it only once Commented Oct 26, 2023 at 15:46
  • What result are you expecting? Commented Oct 26, 2023 at 15:48
  • 5
    Given that it fails for the initial value of 28000 - which is the maximum capacity, maybe check for current_ants < maximum_capacity instead of current_ants <= maximum_capacity? Commented Oct 26, 2023 at 15:49
  • 1
    You want to calculate with the reduced growth rate instead of the regular rate at maximum capacity. Thus use current_ants < maximum_capacity Commented Oct 26, 2023 at 16:07
  • 1
    @slothrop Yes ... it does. I will delete my comment ... Thanks for pointing this out (y) . Commented Oct 26, 2023 at 16:16

2 Answers 2

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0

You are not including the max density. Use < not <= to include it in the check. I also included what I meant in my comment. Plus checking if population it is <= 0 and breaking if so is better than checking if > 0 and continuing to loop:

def count_ants(current_ants, months):
     growth_rate = 0.4 # Monthly growth rate of 40%
     reduced_growth_rate = 0.31 # Reduced monthly growth rate of 31%
     maximum_capacity = 28000 # Maximum capacity of the island
     anteater = 7000 # Number of ants the anteater eats at the end of each month

     for _ in range(months):
         if current_ants <= 0:
             break
         if current_ants < maximum_capacity:
             current_ants += int(current_ants * growth_rate)
         else:
             current_ants += int(current_ants * reduced_growth_rate)
         current_ants -= min(current_ants, anteater)

     return current_ants
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1 Comment

"exceeds the maximum of 28,000". Exceeds is >, not >=. You don't get a ticket for exceeding the speed limit if you are driving the speed limit.
-1

Apparently, this is the only valid solution, to get all the appropriate calculations:

def count_ants(initial_quantity: int, months: int)->int:
     x= 40
     while months!=0:
         if initial_quantity > 28000:
             x= 31
         initial_quantity= initial_quantity+((initial_quantity*x)/100)
         initial_amount= initial_amount-7000
         months= months-1
     if initial_quantity<0:
         initial_quantity= 0
     return round(initial_amount)

Thanks to everyone for your ideas and your help :)

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2 Comments

Not only does this look nothing like the code in your question it just doesn't work. initial_amount referenced before assignment.
This code makes little sense in relation to the original questions posed.

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