Question

This is an interview question.

There are some random numbers given (let’s say in an integer array).

1. How can we sort all the even numbers in ascending order first and then sort all the odd numbers in descending order.
2. which Collection suits best.

Input numbers:

12 67 1 34 9 78 6 31

Output saved in Collection:

6 12 34 78 67 31 9 1 

Answer 1

Any collection that supports sorting with a custom comparer will do – even an array. Implement your custom comparator as follows:

public int compare(int x, int y) {
    if (x&1 == y&1) {
        // Both numbers are odd or both numbers are even
        if (x&1 == 0) {
            // Both numbers are even: compare as usual
            return Integer.compare(x, y);
        } else {
            // Both numbers are odd: compare in reverse
            return Integer.compare(y, x);
        }
    }
    // One is odd, the other one is even
    if (x&1 == 0) {
        return -1;
    }
    return 1;
}