C ++ Roaches项目…消除功能有缺陷

Question

I'm almost done with this program, but something's not right in main . Here are the project instructions:

Assignment:
Write a program which keeps track of the number of roaches in two adjacent houses for a number of weeks. The count of the roaches in the houses will be determined by the following:

1. The initial count of roaches for each house is a random number between 10 and 100.
2. Each week, the number of roaches increases by 30%.
3. The two houses share a wall, through which the roaches may migrate from one to the other. In a given week, if one house has more roaches than the other, roaches from the house with the higher population migrate to the house with the lower population. Specifically, 30% of the difference (rounded down) in population migrates.
4. Every four weeks, one of the houses is visited by an exterminator, resulting in a 90% reduction (rounded down) in the number of roaches in that house.

Here's my code:

#include <iostream>
#include <cmath>
using namespace std;

int house, increase, roaches, filthyBeasts; // My variables for my four functions
int initialCount(int house);
int weeklyIncrease(int increase);
int roachesMigration(int more, int fewer, int change);
int exterminationTime (int filthyBeasts);
// My four function prototypes 

int main()
{
    int houseA, houseB;

    houseA = initialCount(houseA); //Initializing the inital count of House A.
    houseB = initialCount(houseB); //Initializing the inital count of House B.

    int week = 0;
    for (week = 0; week < 11; week++) // My for loop iterating up to 11 weeks.
    {
        houseA = weeklyIncrease(houseA);
        houseB = weeklyIncrease(houseB);

        cout << "For week " << week << ", the total number of roaches in House A is " << houseA << endl;
        cout << "For week " << week << ", the total number of roaches in House B is " << houseB << endl;

        if((houseA > houseB)) // Migration option 1
        {
            houseB = roachesMigration(houseA, houseB);
        }
        else if((houseB > houseA)) // Migration option 2
        {
            houseA = roachesMigration(houseA, houseB);
        }


        if ((week + 1) % 4 == 0) // It's extermination time!
        {
            if ((rand() % 2) == 0) // Get a random number between 0 and 1.
            {
                houseB = exterminationTime(houseB);
            }
            else
            {
                houseA = exterminationTime(houseA);                   
            }
        }
    }

    return 0;
}

int initialCount(int house) // Initializing both houses to random numbers between 10 and 100.
{
    int num;
    num = (rand() % 91) + 10;
    return num;
}

int weeklyIncrease(int increaseHouses) // Increasing the roaches in both houses by 30% weekly.
{
    int increase = 0;
    increase = (increaseHouses * .3) + increaseHouses;
    return increase;
}

int roachesMigration(int more, int fewer, int change)
{
    more -= change;
    fewer += change;   
    return ((more - fewer) * .3);
}


int exterminationTime(int filthyBeasts) // Getting rid of the filthy little beasts!
{
    filthyBeasts = (filthyBeasts * .1);
    return filthyBeasts;
}

There are issues with the migration and extermination functions. I'm receiving an error message from the compiler that says, "error: Semantic Issue: No matching function for call to 'roachesMigration'". Also, at weeks 4 and 8, the randomly selected house should get exterminated, and the number of roaches in that house should be 90% less than the previous week. What do you guys think I should do to correct this issues? I really appreciate all help!

Answer 1

Hint: I notice that you're printing the value of week out at the end of your for loop. In other words, your output should be something like:

For week 0, the total number of roaches in House A is 4
For week 0, the total number of roaches in House B is 5
0
For week 1, the total number of roaches in House A is 6
For week 1, the total number of roaches in House B is 7
1

However, I suspect that the weeks being printed are not what they should be.

Answer 2

Also, your roachesMigration is wrong. It should change the number of roaches in both houses, but not the total number of roaches. It changes the total, but only the number of roaches in one of the houses.

To change both roach counts, you can

1. have the function calculate only the number of roaches that migrate and add/subtract in the main loop
2. have the function change both values, which requires passing them as references or pointers (I'd recommend references here)

For the first option:

int roachesMigration(int more, int fewer)
{
    return ((more - fewer) * 3) / 10;
}

And for the second:

void roachesMigration(int & more, int & fewer)
{
    int migration = ((more - fewer) * 3) / 10;
    more -= migration;
    fewer += migration;
}

If references and pointers have not yet been covered in the course, go with the first option.

Answer 3

Look carefully at what you're doing with the variable "week". Especially, where it is changing value.

Edit: Daniel expanded his answer while I was typing (or I didn't read it completely), so I removed my contribution to the migration.