Description

Submissions

Submission 1

• O(n^2) exceeds the time limit for large test case
• a naive solution

// Complete the arrayManipulation function below.
long arrayManipulation(int n, vector<vector<int>> queries) {
    vector<long> arr(n+1);
    for(int i = 0; i < n+1; ++i) arr[i] = 0;
    for(int i = 0; i < queries.size(); ++i) {
        int a = queries[i][0];
        int b = queries[i][1];
        int k = queries[i][2];
        for(int j = a; j <= b; ++j) {
            arr[j] += k;
        }
    }

    return *max_element(next(arr.begin()), arr.end());
}

Submission 2

• Focus on the less changed value, the differences between consequent numbers
• Only the boundaries being considered

#include <bits/stdc++.h>
#include <limits>

using namespace std;

vector<string> split_string(string);

// Complete the arrayManipulation function below.
long arrayManipulation(int n, vector<vector<int>> queries) {
    vector<int> diff(n+1);
    for(int i = 0; i < n + 1; ++i) diff[i] = 0;

    for(int i = 0; i < queries.size(); ++i) {
        int a = queries[i][0];
        int b = queries[i][1];
        int k = queries[i][2];

        diff[a] += k;
        if(b < n) diff[b+1] -= k;
    }
    long maximum = numeric_limits<int>::min();
    for(long curr = 0, i = 1; i < n + 1; ++i) {
        curr += diff[i];
        if(curr > maximum) maximum = curr;
    }
    return maximum;
}

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

    string nm_temp;
    getline(cin, nm_temp);

    vector<string> nm = split_string(nm_temp);

    int n = stoi(nm[0]);

    int m = stoi(nm[1]);

    vector<vector<int>> queries(m);
    for (int i = 0; i < m; i++) {
        queries[i].resize(3);

        for (int j = 0; j < 3; j++) {
            cin >> queries[i][j];
        }

        cin.ignore(numeric_limits<streamsize>::max(), '\n');
    }

    long result = arrayManipulation(n, queries);

    fout << result << "\n";

    fout.close();

    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/crush/forum/comments/98816?h_l=interview&playlist_slugs%5B%5D=interview-preparation-kit&playlist_slugs%5B%5D=arrays
2. https://www.hackerrank.com/challenges/crush/forum/comments/69550?h_l=interview&playlist_slugs%5B%5D=interview-preparation-kit&playlist_slugs%5B%5D=arrays