Problem with Output in My Median Calculator

Question

bool isEven(int num){
    if(num % 2 == 0){
        return true;
    }
    else {
        return false;
    }
}


int main() {
    int footballPlayer[] = {1,2,3,4};
    int lengthOfArray = sizeof(footballPlayer) / sizeof(footballPlayer[0]);
    int oddMedianFormula = lengthOfArray/2;
    int evenMedianFormula = lengthOfArray/2;
    if(isEven(lengthOfArray) == false) {
         cout << "The median is " << footballPlayer[oddMedianFormula] << endl;
    } else {
        if(isEven(footballPlayer[evenMedianFormula]) == true && isEven(footballPlayer[evenMedianFormula - 1] == true)) {
            cout << "The median is " << (footballPlayer[evenMedianFormula - 1] + footballPlayer[evenMedianFormula]) / 2 << endl;
        }
        else if(isEven(footballPlayer[evenMedianFormula]) == false && isEven(footballPlayer[evenMedianFormula - 1] == false)) {
            cout << "The median is " << (footballPlayer[evenMedianFormula - 1] + footballPlayer[evenMedianFormula]) / 2 << endl;
        }
        else {
            cout << "The median is " << ((footballPlayer[evenMedianFormula - 1] + footballPlayer[evenMedianFormula]) / 2) + 0.5 << endl;
        }
    }

    return 0;
}

output = 2;

Why is my output an integer when one number is odd when I have clearly have added a half (0.5) to the output?

`int` means integer, that's why. You need to change all those `int`s to `float`s except for the `lengthOfArray`. — perreal, Oct 25 '20 at 14:19
@perreal is it recommended to do so even when OP only needs to store int numbers. isn't it better to cast the result instead? — Aniket Kariya, Oct 25 '20 at 14:36
Maybe, but I didn't want to explain all those things in a comment :) — perreal, Oct 25 '20 at 15:57
@perreal Do I also change the type of the array to `double`? and why? — JayYay, Oct 25 '20 at 18:28
Yes. To get a float out of an expression (say a division), at least one of the numbers needs to be a float (this makes the type of the expression float). Also the result should go into a float (or cout is fine too). — perreal, Oct 25 '20 at 19:34

brc-dd · Answer 1 · 2020-10-25T15:51:30.473

When you divide an integer by another integer, you simply get the floor of the mathematical value (as an integer). Say for example : 1 / 2 = (int) floor(0.5) = 0. The answers (they are correct) here have suggested (explicit) type casting your integer values to floating point data types. But I would like to add up something.

You simply can put a point after 2 to make the compiler know you are performing division of floating point numbers. The numerator will be implicitly type converted into double in this case. Don't get confused --> 2. is same as 2.0. Here is your modified code:

#include <iostream>
using namespace std;

bool isEven(int num) {
  if (num % 2 == 0) {
    return true;
  } else {
    return false;
  }
}

int main() {
  int footballPlayer[] = {1, 2, 3, 4};
  int lengthOfArray = sizeof(footballPlayer) / sizeof(footballPlayer[0]);
  int oddMedianFormula = lengthOfArray / 2;
  int evenMedianFormula = lengthOfArray / 2;
  if (isEven(lengthOfArray) == false) {
    cout << "The median is " << footballPlayer[oddMedianFormula] << endl;
  } else {
    if (isEven(footballPlayer[evenMedianFormula]) == true &&
        isEven(footballPlayer[evenMedianFormula - 1] == true)) {
      cout << "The median is "
           << (footballPlayer[evenMedianFormula - 1] +
               footballPlayer[evenMedianFormula]) /
                  2.
           << endl;
    } else if (isEven(footballPlayer[evenMedianFormula]) == false &&
               isEven(footballPlayer[evenMedianFormula - 1] == false)) {
      cout << "The median is "
           << (footballPlayer[evenMedianFormula - 1] +
               footballPlayer[evenMedianFormula]) /
                  2.
           << endl;
    } else {
      cout << "The median is "
           << ((footballPlayer[evenMedianFormula - 1] +
                footballPlayer[evenMedianFormula]) /
               2.) +
                  0.5
           << endl;
    }
  }

  return 0;
}

I don't know why, but your code clearly looks overly complicated to me. I actually doubt if even your logic is correct. If you just want to find the median, then I think this much code will be sufficient:

#include <iostream>
#include <vector>

double findMedianSorted(const std::vector<int> &v) {
  auto n = v.size();
  return n % 2 ? v[n / 2] : (v[(n - 1) / 2] + v[n / 2]) / 2.;
}

int main() {
  std::vector<int> footballPlayer = {1, 2, 3, 4};
  std::cout << "Median is: " << findMedianSorted(footballPlayer);
}

score 0 · Answer 2 · answered Oct 25 '20 at 14:19

0

Because you work with Integers. You have to cast it as Double or Float.

cout << "The median is " << (float)(footballPlayer[evenMedianFormula - 1] + footballPlayer[evenMedianFormula]) / 2 << endl;

Something like this should fix the problem

answered Oct 25 '20 at 14:19

xAqua

11
4

score 0 · Answer 3 · answered Oct 25 '20 at 14:27

That's because you're doing integer division. division of integer types always returns an integer even if the result is in the float. cast any of your variable into float and it should work. What is the behavior of integer division?

Did some changes to your code -

bool isEven(int num)
{
    return !(num % 2);
}

int main()
{
    int footballPlayer[] = {1, 2, 3, 4};
    int lengthOfArray = sizeof(footballPlayer) / sizeof(footballPlayer[0]);

    int oddMedianFormula = lengthOfArray / 2;
    int evenMedianFormula = lengthOfArray / 2;

    if (isEven(lengthOfArray))
    {
        if (isEven(footballPlayer[evenMedianFormula]) && isEven(footballPlayer[evenMedianFormula - 1]))
        {
            cout << "The median is " << (float)(footballPlayer[evenMedianFormula - 1] + footballPlayer[evenMedianFormula]) / 2 << endl;
        }
        else if (!isEven(footballPlayer[evenMedianFormula]) && !isEven(footballPlayer[evenMedianFormula - 1]))
        {
            cout << "The median is " << (float)(footballPlayer[evenMedianFormula - 1] + footballPlayer[evenMedianFormula]) / 2 << endl;
        }
        else
        {
            cout << "The median is " << (float)((footballPlayer[evenMedianFormula - 1] + footballPlayer[evenMedianFormula]) / 2) + 0.5 << endl;
        }
    }
    else
    {
        cout << "The median is " << footballPlayer[oddMedianFormula] << endl;
    }

    return 0;
}

Problem with Output in My Median Calculator

3 Answers3