Homework Question

[Wiebs]

I am stumped on a homework problem and need some help. The constraints of the problem are unique and well...interesting to say the least.

Truly Im confused where to even begin. Below is what I have so far, but some advice on how to structure would be appreciated!

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

//function prototypes
void displayArray(int numbers[], int numElements);
void displayRange(int numbers[], int numElements);
int getMiddle(int numbers[], int numElements);
int getHigh(int numbers[], int numElements);
int getLow(int numbers[], int numElements);

int main()
{
	//declare array
	int randNums[100] = {0};
	int middleNums = 0;
	int highNums = 0;
	int lowNums = 0;

	//initialize RNG
	srand(static_cast<int>(time(0)));
	//assign 100 random integers from 500 through 800 to the array
	for (int sub = 0; sub <100; sub += 1)
		randNums[sub] = 1 + rand() % (800 - 500 + 1);
	//end for

	//system("pause");
	return 0;
}//end of main function

//*function definitions*
void displayArray(int numbers[], int numElements)
{
	for (int sub = 0; sub < numElements; sub +=1)
		cout<<numbers[sub]<<endl;
	//end for
}//end of displayArray function

void displayRange(int number[], int numelements)
{

[yulingo]

You should probably start by using non-random, hard coded arrays to test that your functions are working.

After that, you could either use a sort-and-search approach to be more efficient or a basic approach. I'm guessing from your assignment that you're not expected to use fancy algorithms.

The simplest solution is for each function to have a for loop that iterates over all the array elements, and keeps a running total of the number of elements that match a given condition. For example:

// Count the numbers in the array greater than 560
int count
for (int sub = 0; sub < numElements; ++sub)
{
    if (numbers[sub] > 560)
        ++count;
}

[i like red pandas]

Your rand() function currently produces a random number from 0-300. It should be:
rand() % 301 + 500

[booradley60]

Put a function in your toolkit in case you need to generate numbers in other ranges too:

int getRandInRange(int topOfRange, int bottomOfRange)
{
    if(topOfRange < bottomOfRange)
    {
        int tempForSwap = topOfRange;
        topOfRange = bottomOfRange;
        bottomOfRange = tempForSwap;
    }

    int span = topOfRange - bottomOfRange + 1;
    return (std::rand() % span) + bottomOfRange;
}

I should have restricted this to positive numbers. With a sufficiently large positive topOfRange and a sufficiently small (large negative) bottomOfRange, the subtraction step actually translates to an addition that causes an overflow, yielding the incorrect span. Sometimes this span is zero, resulting in a divide-by-zero error on the modulo calculation.
getRandInRange(std::numeric_limits<int>::max(), std::numeric_limits<int>::min());
Caveat emptor!