HackerRank•May 24, 2025

2D Array - DS

Hazrat Ali

HackerRank

Given a  2D array, , an hourglass is a subset of values with indices falling in the following pattern:

a b c  
  d  
e f g

There are  hourglasses in a  array. The  is the sum of the values in an hourglass. Calculate the hourglass sum for every hourglass in , then print the  hourglass sum.

Example

-9 -9 -9  1 1 1 
 0 -9  0  4 3 2
-9 -9 -9  1 2 3
 0  0  8  6 6 0
 0  0  0 -2 0 0
 0  0  1  2 4 0

The  hourglass sums are:

-63, -34, -9, 12, 
-10,   0, 28, 23, 
-27, -11, -2, 10, 
  9,  17, 25, 18

The highest hourglass sum is  from the hourglass beginning at row , column :

0 4 3
  1
8 6 6

Note: If you have already solved the Java domain's Java 2D Array challenge, you may wish to skip this challenge.

Function Description

Complete the function  with the following parameter(s):

  • : a 2-D array of integers

Returns

  • : the maximum hourglass sum

Input Format

Each of the  lines of inputs  contains  space-separated integers .

Constraints

Sample Input

1 1 1 0 0 0
0 1 0 0 0 0
1 1 1 0 0 0
0 0 2 4 4 0
0 0 0 2 0 0
0 0 1 2 4 0

Sample Output

19

Explanation

 contains the following hourglasses:

image

The hourglass with the maximum sum () is:

2 4 4
  2
1 2 4


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

using namespace std;

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

/*
 * Complete the 'hourglassSum' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts 2D_INTEGER_ARRAY arr as parameter.
 */

int hourglassSum(vector<vector<int>> arr) {
    int max_hourglass = -63;
    for (size_t i = 0; i < arr.size() - 2; i++) {
        for (int j = 2; j < arr[0].size(); j++) {
            int k = j - 2, hourglass = 0;
            while (k <= j) {
                hourglass += arr[i][k] + arr[i + 2][k];
                ++k;
            }
            hourglass += arr[i + 1][j - 1];
            max_hourglass = max(hourglass, max_hourglass);
        }
    }
    return max_hourglass;
}

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

    vector<vector<int>> arr(6);

    for (int i = 0; i < 6; i++) {
        arr[i].resize(6);

        string arr_row_temp_temp;
        getline(cin, arr_row_temp_temp);

        vector<string> arr_row_temp = split(rtrim(arr_row_temp_temp));

        for (int j = 0; j < 6; j++) {
            int arr_row_item = stoi(arr_row_temp[j]);

            arr[i][j] = arr_row_item;
        }
    }

    int result = hourglassSum(arr);

    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;
}




Comments