Solution to Waiter Discussions https://www.hackerrank.com/challenges/waiter/problem

waiters.java

public static int[] firstQPrimes(int q) {
        /*
         * Write your code here.
         */
        // Generar primeros q numeros primos con la criba de atkin
        //hay 1229 numeros primos entre 1 y 10000
        int limit = q;
        boolean sieve[] = new boolean[limit];
        if(limit > 2) sieve[2] = true;
        if(limit > 3) sieve[3] = true;
        
        
        for(int x=1;x*x<limit;x++){
            for(int y=1;y*y<limit;y++){
                int n = (4*x*x) + (y*y);
                if(n<= limit && (n%12 == 1 || n%12 == 5)){
                    sieve[n] ^= true;
                }
                n = (3*x*x) + (y*y);
                if(n<=limit && n%12 == 7){
                    sieve[n] ^= true;
                }
                n = (3*x*x) - (y*y);
                if(x > y && n<=limit && n%12 == 11){
                    sieve[n] ^= true;
                }
            }
        }
        for(int r = 5;r*r < limit;r++){
            if(sieve[r]){
                for(int i=r*r;i<limit;i+=r*r){
                    sieve[i] = false;
                }
            }
        }
        int l = 1208;
        int [] primes = new int[l];
        int top = 0;
        for(int i=0;i<sieve.length;i++){
           if(sieve[i]){
               primes[top++] = i;
           }
        }
        return primes;
    }
    static int[] waiter(int [] number,int q) {
        //Genera primeros 1200 primos
        int [] primes = firstQPrimes(9800);
        int [] finale = new int[number.length];
        int top = 0;
        boolean orden = true;
        for(int i=0;i<q;i++){
            if(orden){
                for(int j=0;j<number.length;j++){
                    if(number[j]%primes[i] == 0){
                        finale[top++] = number[j];
                        //System.out.println(number[j]);
                        number[j] = -1;
                    }
                }
            }
            else{
                for(int j=number.length-1;j>=0;j--){
                    if(number[j]%primes[i] == 0){
                        finale[top++] = number[j];
                        //System.out.println(number[j]);
                        number[j] = -1;
                    }
                }
            }
            orden ^= true;
        }
        orden ^= true;
        if(orden){
            for(int j=0;j<number.length;j++){
                if(number[j] != -1){
                    finale[top++] = number[j];
                    //System.out.println(number[j]);
                }
            }
        }
        else{
            for(int j=number.length-1;j>=0;j--){
                if(number[j] != -1){
                    finale[top++] = number[j];
                    //System.out.println(number[j]);
                }
            }
        }
        
        //number es A_0
        return finale;
    }