function icecreamParlor(m, arr) {
    // Write your code here
    let results = {};
    
    for(let i = 0; i <= arr.length; i++){
        if(results.hasOwnProperty(arr[i])) {
            return [results[arr[i]] + 1, i + 1]
        }

        results[m - arr[i]] = i;
    }
}

use std::collections::HashMap;
fn icecreamParlor(m: i32, arr: &[i32]) -> Vec<i32> {
    let mut map = HashMap::new();
    arr.iter().enumerate().fold((0, vec![]), |(i, res), (j, &x)| {
        if res.is_empty() && map.contains_key(&(m - x)) {
            (i + 1, vec![map[&(m - x)], j as i32 + 1])
        } else {
            map.entry(x).or_insert(j as i32 + 1);
            (i + 1, res)
        }
    }).1
}

vector<int> icecreamParlor(int m, vector<int> arr) {
    vector<int> res;
    vector<ii> v;
    for (int i = 0; i < arr.size(); i++) v.push_back(ii(arr[i], i + 1));
    sort(v.begin(), v.end());
    int rem, ind;
    for (int i = 0; i < v.size(); i++){
        rem = m - v[i].first;
        ind = lower_bound(v.begin() + i + 1, v.end(), ii(rem, 0)) - v.begin();
        if (v[ind].first == rem){
            res.push_back(v[i].second);
            res.push_back(v[ind].second);
            break;
        }
    }
    sort(res.begin(), res.end());
    return res;
}