Here is a Java solutions that runs in O(n)

public static void main(String[] args) {

    Scanner scan = new Scanner(System.in);
    int n = scan.nextInt();

    for(int i = 0; i < n; i++){

        int cost = scan.nextInt();
        int size = scan.nextInt();
        int prices[] =  new int[size];

        for(int j = 0; j < size; j++){
            prices[j] = scan.nextInt();
        }

        determineFlavors(prices,cost);

    }

}

public static void determineFlavors(int prices[], int maxCost){

    HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();

    map.put(prices[0],1);

    for(int i = 1; i < prices.length; i++){

        Integer k = map.get(maxCost - prices[i]);

        if(k == null){
            map.put(prices[i], i+1);
        }else{
            System.out.println(k + " " + (i+1));
            break;    
        }

    }

}