Need a fix for this implicit cast error in my find median method

Question

Need to find a fix to this implicit cast error to get the code to compile. The code is:

// Program calls a method that finds and returns
// the median value in an array
// The median value is the middle value from largest to smallest
// If there are an even number of values, the
// median is the mean of the two middle values
using System;
using static System.Console;
class DebugSeven4
{
    static void Main()
    {
        double[] firstArray = { 10, 9, 2, 3, 5, 6 };
        double[] secondArray = { 112, 456, 782 };
        double[] thirdArray = { 9, 12, 45, 82, 84, 67, 2, 6 };
        WriteLine("The median value of the first array is {0}",
           FindMedian(firstArray));
        WriteLine("The median value of the second array is {0}",
           FindMedian(secondArray));
        WriteLine("The median value of the third array is {0}",
           FindMedian(thirdArray));
    }
    private static double FindMedian(double[] array)
    {
        double median;
        double middle = array.Length / 2;
        Array.Sort(array);
        if (array.Length % 2 == 0)
            median = (double)(array[middle - 1] + array[middle]) / 2;
        else
            median = (double) array[middle];
        return median;
    }
}

The error is "Cannot implicit convert type double to int. Could be missing a cast." but I'm not certain that's the actual problem. It appears to be complaining about the middle variable.

Not sure *any* of the proposed duplicates are actually duplicates. Despite the question, this really has nothing to do with converting to an integer, the variable (an array index) should never have been floating point in the first place. — paxdiablo, Oct 22 '19 at 00:01
@Keith, despite the title of this question, it has *nothing* to do with converting a double to an int. The variable, which is an array index, should never have been a double in the first place. I'd had this discussion previously with mjwills. Will try to edit to make that clearer. — paxdiablo, Oct 22 '19 at 03:40

score 4 · Answer 1 · answered Oct 21 '19 at 23:59

4

Re:

double middle = array.Length / 2;

Since array indexes are integers anyway, that should probably just be an integer:

int middle = array.Length / 2;

Then the casting problem just goes away.

answered Oct 21 '19 at 23:59

paxdiablo

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John Alexiou · Answer 2 · 2022-10-09T06:09:02.077

middle variable needs to be an integer since it is actually the index of the middle, and not a value itself.

private static double FindMedian(double[] array)
{
    double median;
    int middleIndex = array.Length / 2;
    Array.Sort(array);
    if (array.Length % 2 == 0)
        median = (array[middleIndex-1] + array[middleIndex]) / 2;
    else
        median = array[middleIndex];
    return median;
}

I also removed all necessary castings. Since the results of array[i] is a double there is no need to cast it again as a double after you divide by an integer, like array[i]/2 as the compiler is going to implicitly convert the integer into a double and do the division with also a double as the result.

You can further simplify the code with the return keyword

private static double FindMedian(double[] array)
{
    int middleIndex = array.Length / 2;
    Array.Sort(array);
    if (array.Length % 2 == 0)
    {
        return (array[middleIndex - 1] + array[middleIndex]) / 2;
    }
    else
    {
        return array[middleIndex];
    }
}

or just with the tertiary operator

private static double FindMedian(double[] array)
{
    int middleIndex = array.Length / 2;
    Array.Sort(array);
    return array.Length % 2 == 0 ? (array[middleIndex - 1] + array[middleIndex]) / 2 : array[middleIndex];
}

Need a fix for this implicit cast error in my find median method

2 Answers2