function icecreamParlor(m: number, arr: number[]): number[] {
  let obj = {} as any;

  for (let i = 0; i < arr.length; i++) {
    obj[arr[i]] = i;
  }

  for (let j = 0; j < arr.length; j++) {
    const target = m - arr[j];
    if (obj[target] && obj[target] !== j) {
      return [j + 1, obj[target] + 1];
    }
  }

  return [];
}

public static List<Integer> icecreamParlor(int m, List<Integer> arr) {
        Map<Integer, Integer> flavorMap = new HashMap<>();
        
        for (int i = 0; i < arr.size(); i++) {
            int currentFlavorCost = arr.get(i);
            int complementCost = m - currentFlavorCost;
            
            if (flavorMap.containsKey(complementCost)) {
                return Arrays.asList(flavorMap.get(complementCost) + 1, i + 1);
            }
            
            flavorMap.put(currentFlavorCost, i);
        }
        
        return null; 
    }

def icecreamParlor(m, arr):
    for i,e in enumerate(arr):
        n = (arr[:i]+arr[i+1:])
        if m-e in n:
            return [i+1, n.index(m-e)+2]

vector<int> icecreamParlor(int m, vector<int> arr){
    vector <int> result;
    int expense_left; 
    for (int i = 0; i < arr.size(); i++){
        expense_left = m - arr[i]; // for every entry, calculate expense left
        auto search = find(arr.begin()+i+1, arr.end(), expense_left); // see if expense left is available
        
        //if expense left is available, return 1-based index
        if (search != arr.end()){
            result.push_back(i+1);
            result.push_back(search-arr.begin()+1); // search-arr.begin() gives 0-based indexing, so add 1
            break;
        }
    }
    return result;    
}

public static List<Integer> icecreamParlor(int m, List<Integer> arr) {
        for (int i = 0; i < arr.size(); i++) {
            if (arr.subList(i + 1, arr.size()).contains(m - arr.get(i))) {
                return Stream.of(i + 1, arr.lastIndexOf(m - arr.get(i)) + 1).sorted().collect(Collectors.toList());
            }
        }
        
        // WTF?
        return null;
    }