solution.cpp

#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);
vector<string> split(const string &);

/*
 * The function is expected to return a LONG_INTEGER.
 * The function accepts INTEGER_ARRAY prices as parameter.
 */

// Implementation Part
long stockmax(vector<int> prices) {
    
        long profit = 0;
        int maxPrice = 0;
        
        // checking from back of vector and find possible max price
        for (int i = prices.size() - 1; i >= 0 ; i--) {
            // if current price is greater than max price then,
            // update max price with current price 
            if (prices[i] >= maxPrice) {
                maxPrice = prices[i];
            }
            
            // calculate profit
            profit += maxPrice - prices[i];
        }
        return profit;
}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string t_temp;
    getline(cin, t_temp);

    int t = stoi(ltrim(rtrim(t_temp)));

    for (int t_itr = 0; t_itr < t; t_itr++) {
        string n_temp;
        getline(cin, n_temp);

        int n = stoi(ltrim(rtrim(n_temp)));

        string prices_temp_temp;
        getline(cin, prices_temp_temp);

        vector<string> prices_temp = split(rtrim(prices_temp_temp));

        vector<int> prices(n);

        for (int i = 0; i < n; i++) {
            int prices_item = stoi(prices_temp[i]);

            prices[i] = prices_item;
        }

        long result = stockmax(prices);

        fout << result << "\n";
    }

    fout.close();

    return 0;
}

string ltrim(const string &str) {
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str) {
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

vector<string> split(const string &str) {
    vector<string> tokens;

    string::size_type start = 0;
    string::size_type end = 0;

    while ((end = str.find(" ", start)) != string::npos) {
        tokens.push_back(str.substr(start, end - start));

        start = end + 1;
    }

    tokens.push_back(str.substr(start));

    return tokens;
}