Drop lowest input from Array? - c++

Question

I have to find the lowest input given, then average out the total minus the lowest score. I am having a bit of trouble with my averageScore function finding the lowest score from the array. I am getting very odd numbers as my output. Any suggestions on how to adjust this would be appreciated. Thanks in advance.
#include <iostream>
#include <cstdlib>
using namespace std;
//function prototypes
double* allocate(int&);
double averageScore(int&);
int main()
{
double* testArray;
int numOfScores;
double average;
testArray = allocate(numOfScores);
average = averageScore(numOfScores);
//delete memory created
delete[] testArray;
return 0;
}
//function to collect user info, dynamically allocate
double* allocate(int &numOfScores)
{
double* testArray;
//prompt user for scores
cout << "How many test scores would\n";
cout << "you like to process: ";
//user input validation
if(!(cin >> numOfScores))
{
cout << "Invalid input!\n";
cout << "Program termination, please\n";
cout << "restart the program." << endl;
exit(0);
}
else if(numOfScores < 0)
{
cout << "Invalid input!\n";
cout << "Program termination, please\n";
cout << "restart the program." << endl;
exit(0);
}
//dynammically allocate an arrray to hold the scores
testArray = new double[numOfScores];
//get the scores from user
for (int count = 0; count < numOfScores; count++)
{
cout << "Enter Score: ";
//user input validation
if(!(cin >> testArray[count]))
{
cout << "Invalid input!\n";
cout << "Program termination, please\n";
cout << "restart the program." << endl;
exit(0);
}
else if(testArray[count] < 0.0)
{
cout << "Invalid input!\n";
cout << "Program termination, please\n";
cout << "restart the program." << endl;
exit(0);
}
}
return testArray;
}
//function to calculate the average score
double averageScore(int &numOfScores)
{
double* testArray;
double total,
average,
scores[0],
lowest;
lowest = scores[0];
//calculate total scores entered
for(int count = 0; count < numOfScores; count++)
{
total += testArray[count];
//find lowest score entered
for(int count = 1; count < numOfScores; count++)
{
if (testArray[numOfScores] < lowest)
lowest = scores[numOfScores];
}
}
//average the total amount of scores drop the lowest
average = (total - lowest) / numOfScores;
cout << "The average test score is: " << average << endl;
cout << "Lowest is: " << lowest << endl;
return average;
}

Answer 1

std::vector<double> scores = {1.2,6.5,3.0,8.3,4.8,6,7.7};
// drop lowest score
scores.erase(min_element(begin(scores),end(scores)));
double average = accumulate(begin(scores),end(scores),0.0)/scores.size();

Answer 2

Couple issues. You shouldnt have those two for loops nested(instead just check if the value is lower than the lowest using an if statement).
Since this is homework I will give you the steps and then you can fix your code
Loop through and calculate the total, finding the lowest score at the same time
Calculate the average as (total-lowest)/(numScores -1)
Return the average

Answer 3

I think you want to change this line:
if(testArray[numOfScores] < lowest)
to this:
if(testArray[count] < lowest)
Also, as #jzworkman points out, the denominator for averaging should be (numScores - 1) since you are eliminating the lowest score from the numerator. (If applicable, you might want to test for the edge case where there is only one score, which leaves nothing to average once you eliminate the lowest score.)

Answer 4

There are a lot of problems with your averageScore function, but i'll cover the most basic one for now.
First off, you should pass it some sort of data. Right now you're using testArray I don't even see where it is allocated. I'm surprised that you're not getting segmentation faults when you run this.
But it's also not initialized. In c++, when you declare a pointer, the variable it points to has a value. It has a garbage value, and if you perform arithmetic operations with that garbage value, then your output will be garbage too.
You have to make your list of scores available to your averageScore function, preferably by passing them in as a parameter.
the beginning of your averaging function looks like the following:
double averageScore(int &numOfScores)
{
double* testArray;
...
instead it should look like this
double averageScore(double*testArray, int numOfScores)
{
...
when you use &numOfScores instead of numOfScores, that means that if you change numOfScores in your averageScore function, than it will change in your main function as well, and you shouldn't do that.
now, on the double* testArray; line, you're declaring a brand new pointer, named "testArray", and there's no meaningful data in it, although it might be full of garbage. there might be other double pointer variables, named "testArray" in your code, but none of them are in the scope of your averageScore function. If you pass testArray in, in your method call, you'll then be able to use it. for example: double someNumber = testArray[i].
Bare in mind that your array is also being passed by reference. If you would rather pass it by value, you can try
`double averageScore(double testArray[], int numOfScores)`
but don't quote me on that one
Once you've done that, your code will still have some issues, but the output should be meaningful enough that you'll hopefully be able to work those out on your own.