Finding min/max with calculated values

Method getMaxEvenOdd returns the maximum amount by which the number of even elements exceeds the number of odd elements during a left to right traversal of arr. The method returns 0 if the number of even elements never exceeds the number of odd elements.

getMaxEvenOdd examples

int[] arr1 = new int[] {4, 6, 1, 4, 3, 4, 4, 7};
//              index:  0  1  2  3  4  5  6  7
//         even - odd:  1  2  1  2  1  2  3  2
    
System.out.println(MaxEvenOdd.getMaxEvenOdd(arr1)); // prints 3


int[] arr2 = new int[] { 5,  7,  2,  5,  4,  3,  3,  8};
//              index:   0   1   2   3   4   5   6   7
//         even - odd:  -1  -2  -1  -2  -1  -2  -3  -2  

System.out.println(MaxEvenOdd.getMaxEvenOdd(arr2)); // prints 0

For each array, the number under each index represents the difference between the number of even elements and the number of odd elements up to and including the element at that index. A positive number indicates more even elements.

There are 3 even elements and 1 odd element up to and including the value at arr1[3]. There are 5 even elements and 2 odd elements up to and including the value at arr1[6].

There are 2 even elements and 3 odd elements up to and including the value at arr2[4].

getMaxEvenOdd(arr1) returns 3 because the difference between the number of even and odd elements reaches 3 after visiting the element at index 6.

getMaxEvenOdd(arr2) returns 0 because the number of even elements never exceeds the number of odd elements.

getMaxEvenOdd method & explanation

public static int getMaxEvenOdd(int[] arr)
{
    int difference = 0;
    int maxDifference = 0;
    
    for(int i = 0; i < arr.length; i++)
    {
        if(arr[i] % 2 == 0)
            difference++;
        else
            difference--;
        
        if(difference > maxDifference)
            maxDifference = difference;
    }
    
    return maxDifference;
}

difference stores the difference between the number of known even values and the number of known odd values. A positive number indicates more even values.

maxDifference stores the maximum known difference, or 0 if the number of even values has never exceeded the number of odd values.

Initializing maxDifference to 0 is appropriate for several reasons.

Comments

Comment on Finding the minimum or maximum