how to calculate mode for a sorted array in java

Question

So I'm writing a method to calculate mode of a sorted array. But when i print out the mode value, it always comes out as 0.00, and i tried to fix it but could't. Here's my code for this method: (numRead is the passed array, num is the array length that actually have values)

public static void modeCalc(double[] numRead, int num)
    {
        double maxValue = numRead[0];
        int maxCount = 0;
        for (int i = 0; i < numRead.length; i++)
        {
            int count = 0;
            for (int j = 0; j < numRead.length; j++)
            {
                if (numRead[j] == numRead[i])
                    count++;
            }
            if (count > maxCount)
            {
                maxCount = count;
                maxValue = numRead[i];
            }
        }
        return maxValue;
    }

Any help is much appreciated!

Answer 1

This should work. You need to return a double, and you need to use num.

class ModeArray
{
    public static void main(String[] args) {
        double[] numRead = { 1, 2, 3, 3, 4, 4, 4, 5, 0, 0, 0, 0, 0 };
        System.out.println(modeCalc(numRead, 8));
    }

    public static double modeCalc(double[] numRead, int num) {
        double maxValue = numRead[0];
        int maxCount = 0;
        for (int i = 0; i < num; i++) {
            int count = 0;
            for (int j = 0; j < num; j++) {
                if (numRead[j] == numRead[i]){
                    count++;
                }
            }
            if (count > maxCount) {
                maxCount = count;
                maxValue = numRead[i];
            }
        }
        return maxValue;
    }
}

If you know the array is sorted, you should use this information.

public static double modeCalc(double[] numRead, int num) {
    double maxValue = numRead[0];
    double lastValue = maxValue;
    int count = 1;
    int maxCount = 1;
    for (int i = 1; i < num; i++) {
        if (numRead[i] == lastValue) {
            count++;
        } else {
            count = 1;
            lastValue = numRead[i];
        }
        if (count > maxCount) {
            maxCount = count;
            maxValue = lastValue;
        }
    }
    return maxValue;
}

PS: Please don't use if-statement without braces. It makes it easier to add bugs, and harder to find them.