Question

Ok the only problem with this program is at the end where I try to decide which months rain totals were lowest or highest. My output for either works great UNLESS “Jan”(January) is either the highest or lowest.Then either will just be left blank. All other variations work great. Any idea as to why this is happening? Is an index of my array off somewhere? Thanks in advance for any advice.

#include <iostream>
#include <string>
#include <iomanip>
#include <cstdlib>
using namespace std;

int main()
{
    //declare and initialize variable and arrays
    string year[] = {"Jan", "Feb", "Mar", "April", "May", "June",
            "July", "August", "Sept", "Oct", "Nov", "Dec"}; 

    const int totalMonths = 12;

    double month[totalMonths]; 

    double average; 
    double total = 0;

    cout << "This program will calculate the total annual rainfall,\n";
    cout << "calculate the monthly average rainfall, and display\n";
    cout << "which month had the lowest amount of rainfall and which\n";
    cout << "month had the highest amount of rainfall. Please enter the\n";
    cout << "rainfall data in inches." << endl;
    cout << "----------------------------------------------------------" << endl;

    // prompt user for input, keep a total sum of data entered
    for(int i = 0; i < 12; i++)
    {
        cout << "Enter total rainfall for " << year[i] << endl;
        cin >> month[i];
        total += month[i];
    while(month[i] < 0)
    {
        cout << "Rainfall cannot be negative!\n";
        cout << "Please re-enter positive numbers" << endl;
        cin >> month[i];
    }       

    }

    //average the total rainfall
    average = total / totalMonths;

    cout << setprecision(1) << fixed;
    cout << "Total Annual rainfall is: " << total << endl;
    cout << "The average rainfall per month is: " << average << endl;

    //determine which month had the lowest and highest amount of rainfall
    double highest = 0;
    string highMonth;
    highest = month[0];
    for(int count = 0; count < totalMonths; count++)
    {
        if(month[count] > highest)
        {
            highest = month[count];
            highMonth = year[count];

        }

    }

    double lowest = 0;
    string lowMonth;
    lowest = month[0];
    for(int count = 0; count < totalMonths; count++)
    {
        if(month[count] < lowest)
        {
            lowest = month[count];
            lowMonth = year[count];
        }
    }

    cout << "The month with the highest rainfall is: " << highMonth << endl;
    cout << "The month with the lowest rainfall is: " << lowMonth << endl;  

return 0;
}

Example of the output:

This program will calculate the total annual rainfall,
calculate the monthly average rainfall, and display
which month had the lowest amount of rainfall and which
month had the highest amount of rainfall. Please enter the
rainfall data in inches.
----------------------------------------------------------
Enter total rainfall for Jan
1
Enter total rainfall for Feb
2
Enter total rainfall for Mar
3
Enter total rainfall for April
4
Enter total rainfall for May
5
Enter total rainfall for June
6
Enter total rainfall for July
7
Enter total rainfall for August
89
Enter total rainfall for Sept
12
Enter total rainfall for Oct
13
Enter total rainfall for Nov
14
Enter total rainfall for Dec
15
Total Annual rainfall is: 171.0
The average rainfall per month is: 14.2
The month with the highest rainfall is: August
The month with the lowest rainfall is: <-------- //BLANK!

Answer 1

I spotted two issues in this program:

1. The reason why you’re here — you’re not allowing the first month to match:

   double highest = 0;
   string highMonth;
   highest = month[0];
   for(int count = 0; count < totalMonths; count++)
   {
       if(month[count] > highest)
       {
           highest = month[count];
           highMonth = year[count];
       }
   }
   

   In this case, the month[count] > highest test can never be true for January. Amend the test:

       if(month[count] >= highest)
   

   This allows the first month to match. Keep this in mind, you’ll probably make this mistake again — I know I have. (The fix is similar for the other case.)

2. Another issue you haven’t run into yet, but I’m sure your professor will notice: you don’t handle negative numbers correctly:

   for (int i = 0; i < 12; i++)
   {
       cout << "Enter total rainfall for " << year[i] << endl;
       cin >> month[i];
       total += month[i];
       while (month[i] < 0)
       {
           cout << "Rainfall cannot be negative!\n";
           cout << "Please re-enter positive numbers" << endl;
           cin >> month[i];
       }
   }
   

   What happens if the user types in a negative number? The total += month[i] line will still influence the total (and thus the average), even though your output claims to disallow negative numbers. This might be difficult to spot during simple hand-testing unless you also hand-calculate the correct numbers, too. (Hint: when you can check input against hand-calculated results, it’s almost always worthwhile.)