I need help to sort numbers in an array in ascending and descending order. Even numbers should be ascending and odd numbers descending.

I have managed to sort the number in ascending order but want to do the opposite for the odd numbers.

Actual Results: Both odd and even numbers ascending

Expected Results: Even numbers ascending and odd numbers descending

System.out.println("\n"   "random numbers generated:");
System.out.println(Arrays.toString(arrayList).replace("[", "").replace("]", "").replace(",", ""));
for (int i = 0; i < arrayList.length; i  ) {
    for (int j = i 1; j < arrayList.length; j  ) {
        if(arrayList[i] > arrayList[j]) {
            temporaryArray = arrayList[i];
            arrayList[i] = arrayList[j];
            arrayList[j] = temporaryArray;
        }
    }
}
System.out.println("\n"   "random numbers arranged:");

int[] arrayTwo = Arrays.copyOf(arrayList, arrayList.length);

for (int i = 0; i < arrayList.length; i  ) {
    if(arrayTwo[i]%2!=0) {
        System.out.print(arrayTwo[i]   " ");
    }
}

System.out.print("| ");

for (int i = 0; i < arrayList.length; i  ) {
    if(arrayTwo[i]%2==0) {
        System.out.print(arrayTwo[i]   " ");
    }
}

How can I reverse array for odd numbers?

CodePudding user response：

I would recommend that you :

• 1. sort all numbers in ascending order,
• 2. extract the odd numbers to a second array and
• 3. reverse this new array. Manipulating two different orderings in a same array would prove much more complicated. On a side note, if you don't have a requirement not to, I'd recommend using the Arrays library's Arrays.sort() to simplify your code. It is very readable and has lower complexity of O(N log N).

CodePudding user response：

What you can do is write a recursive function like so:

public static void printOddReversed(int[] array, int index) {
    if (index == array.length)
        return;

    printOddReversed(array, index   1);

    if (array[index] % 2 != 0) {
        System.out.print(array[index]   " ");
    }
}

and then instead of the third loop, call it like so:

printOddReversed(arrayTwo, 0);

CodePudding user response：

A simple way to do that is by using a special comparator:

        if (a%2 == 0) {
            if (b%2 == 0) {
                return Integer.compare(a,b);
            } else {
                return -1;
            }
        } else {
            if (b%2 == 0) {
                return 1;
            } else {
                return Integer.compare(b, a);
            }
        }

UPDATE: Example

    int[] arrayList = {959, 321, 658, 3, 506, 165, 560, 582, 199, 533, 178};
    for (int i = 0; i < arrayList.length; i  ) {
        for (int j = i 1; j < arrayList.length; j  ) {
            if(compare(arrayList[i], arrayList[j]) > 0) {
                int temporaryArray = arrayList[i];
                arrayList[i] = arrayList[j];
                arrayList[j] = temporaryArray;
            }
        }
    }

    System.out.println(Arrays.toString(arrayList));

...

private static int compare(int a, int b) {
    if (a%2 == 0) {
        if (b%2 == 0) {
            return Integer.compare(a,b);
        } else {
            return -1;
        }
    } else {
        if (b%2 == 0) {
            return 1;
        } else {
            return Integer.compare(b, a);
        }
    }
}