Finding a median (double) in C++ Array?

Question

This website is my last resort. I am working on an assignment for my intro to CS class. I am to write a function that takes two parameters (an array of int and the size of the array). The function should return the median of the array. Array has been sorted using the built-in sort function from the examples in this week's module. Here is my code (so far):

#include<iostream>
#include<algorithm>
using std::cout;
using std::endl;

//Function prototype
double findMedian(int array[], int size);

//Main function
int main()
{
    int array[] = {23, 5, -10, 0, 0, 321, 1, 2, 99, 30};
    int size = 10;

    //Function to sort array smallest to largest
    std::sort(array, array + size);
    for(int i = 0; i < size; i++)
       std::cout << array[i] << ' ' ;

    //Call to findMedian function
    double median = findMedian(array, size);

    //Output median of the array
    std::cout << "\nMedian is: " << median << std::endl;

    return 0;
}

//Function to calculate median of sorted array
double findMedian(int array[], int size)
{
    double median = 0.0;

    if(size % 2 == 0) //If array size is even
    {
        median = (array[(size-1)/2] + array[size/2])/2.0;
    }
    else //If array size is odd
    {
    median = array[size/2];
    }
    return median;
}

I am submitting the assignment through Mimir and it has now failed the first three submissions, with the following message:

INPUT OF THE TEST CASE 
#include <cmath>
const double EPS = 0.00001;

int array[] = {1,5,7,4,2,6,3,9,8};
double result = findMedian(array, 9);
ASSERT_TRUE(fabs(result-5.0) < EPS);


YOUR CODE'S OUTPUT 
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from MimirTest
[ RUN      ] MimirTest.cppUnitTest
tests.cpp:24: Failure
Value of: fabs(result-5.0) < EPS
  Actual: false
Expected: true
[  FAILED  ] MimirTest.cppUnitTest (0 ms)
[----------] 1 test from MimirTest (0 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test case ran. (0 ms total)
[  PASSED  ] 0 tests.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] MimirTest.cppUnitTest

1 FAILED TEST

I am not entirely sure where the error in my code is that is causing this test failure. Any pointers would be much appreciated! This is an intro class, so I am only allowed to use the methods covered so far (Gaddis Intro to Object-Oriented Programming Chapters 1-8). THANK YOU!

Possible duplicate of [Compute Median of Values Stored In Vector - C++?](https://stackoverflow.com/questions/2114797/compute-median-of-values-stored-in-vector-c) — , Nov 05 '18 at 01:12

score 3 · Accepted Answer · answered Nov 05 '18 at 00:34

3

Your findMedian function assumes that the array is already sorted. But the array in the test case that fails isn't.

answered Nov 05 '18 at 00:34

Henning Koehler

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Adding to this, you can see from the test code running that it calls the findMedian() function directly. None of the code in main() will be run. You can use main() for your testing, but all your work must be in findMedian(). – lod Nov 05 '18 at 03:43
That's exactly it! Thank you. And for submission, we need to comment out the main and in doing so, I also commented out the sort function within it. I ended up moving the sort down to findMedian, as well as incorporating test case variable (const double EPS = 0.00001;) and (if(fabs(median-5.0) < EPS) statement to return "true" or "false" based on sort/no sort. Thanks again! – strawberry_shortcakes Nov 05 '18 at 10:32

Finding a median (double) in C++ Array?

1 Answers1