Description

• Any O(n^2) algorithm will exceed the time limit

Submission

Submission 1

• Bubble Sort: O(n^2), exceeds the time limit for large n’s
• The count should be of size q.size()+1

#include <bits/stdc++.h>

using namespace std;

vector<string> split_string(string);

// Complete the minimumBribes function below.
void minimumBribes(vector<int> q) {
    vector<int> count(q.size() + 1);
    int total = 0;

    for(int i = 0; i < count.size(); ++i) count[i] = 0;

    for(int i = 0; i < q.size() - 1; ++i) {
        for(int j = q.size() - 1; j > i; --j) {
            if(q[j] < q[j-1]) {
                swap(q[j], q[j-1]);
                total++;

                if(++count[q[j]] > 2) {
                    cout << "Too chaotic\n";
                    return;
                }   
            }  
        }
    }
    cout << total << endl;
}

int main()
{
    int t;
    cin >> t;
    cin.ignore(numeric_limits<streamsize>::max(), '\n');

    for (int t_itr = 0; t_itr < t; t_itr++) {
        int n;
        cin >> n;
        cin.ignore(numeric_limits<streamsize>::max(), '\n');

        string q_temp_temp;
        getline(cin, q_temp_temp);

        vector<string> q_temp = split_string(q_temp_temp);

        vector<int> q(n);

        for (int i = 0; i < n; i++) {
            int q_item = stoi(q_temp[i]);

            q[i] = q_item;
        }

        minimumBribes(q);
    }

    return 0;
}

vector<string> split_string(string input_string) {
    string::iterator new_end = unique(input_string.begin(), input_string.end(), [] (const char &x, const char &y) {
        return x == y and x == ' ';
    });

    input_string.erase(new_end, input_string.end());

    while (input_string[input_string.length() - 1] == ' ') {
        input_string.pop_back();
    }

    vector<string> splits;
    char delimiter = ' ';

    size_t i = 0;
    size_t pos = input_string.find(delimiter);

    while (pos != string::npos) {
        splits.push_back(input_string.substr(i, pos - i));

        i = pos + 1;
        pos = input_string.find(delimiter, i);
    }

    splits.push_back(input_string.substr(i, min(pos, input_string.length()) - i + 1));

    return splits;
}

Submission 2

• Find the number of occurrences of people overtaking over other people
• Since the “Too chaotic” part guarantees that the overtake won’t exceed 2, we can safely search from q[i]-2, to make it safe max(0, q[i] – 2)

#include <bits/stdc++.h>

using namespace std;

vector<string> split_string(string);

// Complete the minimumBribes function below.
void minimumBribes(vector<int> q) {
    int count = 0;
    for(int i = 0; i < q.size(); ++i) {
        if(q[i]-1-i > 2) {
            cout << "Too chaotic\n";
            return;
        }
        for(int j = max(0, q[i] - 2); j < i; ++j) {
            if(q[j] > q[i]) count++;
        }
    }
    cout << count << endl;
}

int main()
{
    int t;
    cin >> t;
    cin.ignore(numeric_limits<streamsize>::max(), '\n');

    for (int t_itr = 0; t_itr < t; t_itr++) {
        int n;
        cin >> n;
        cin.ignore(numeric_limits<streamsize>::max(), '\n');

        string q_temp_temp;
        getline(cin, q_temp_temp);

        vector<string> q_temp = split_string(q_temp_temp);

        vector<int> q(n);

        for (int i = 0; i < n; i++) {
            int q_item = stoi(q_temp[i]);

            q[i] = q_item;
        }

        minimumBribes(q);
    }

    return 0;
}

vector<string> split_string(string input_string) {
    string::iterator new_end = unique(input_string.begin(), input_string.end(), [] (const char &x, const char &y) {
        return x == y and x == ' ';
    });

    input_string.erase(new_end, input_string.end());

    while (input_string[input_string.length() - 1] == ' ') {
        input_string.pop_back();
    }

    vector<string> splits;
    char delimiter = ' ';

    size_t i = 0;
    size_t pos = input_string.find(delimiter);

    while (pos != string::npos) {
        splits.push_back(input_string.substr(i, pos - i));

        i = pos + 1;
        pos = input_string.find(delimiter, i);
    }

    splits.push_back(input_string.substr(i, min(pos, input_string.length()) - i + 1));

    return splits;
}

References

1. https://www.hackerrank.com/challenges/new-year-chaos/forum/comments/143969?h_l=interview&playlist_slugs%5B%5D=interview-preparation-kit&playlist_slugs%5B%5D=arrays