HackerRank Diagonal Difference Solution

Problem Statement

Given a square matrix[NxN], calculate the absolute difference between the sums of its diagonals.

Sample Input

3
11  2  4
4   5  6
10  8 -12

Sample Output

15

Diagonal(Primary Diagonal)

11
  5
   -12

Anti-Diagonal(Secondary Diagonal)

    4
  5
10

The absolute difference of sum of Diagonal and Anti-Diagonal elements

Diagonal Sum = 11+5+(-12) = 4
Anti-Diagonal Sum = 4+5+10 = 19

Diagonal Difference : |4-19| = 15

Let's move code side

Here's the function diagonalDifference

int diagonalDifference(vector<vector<int>> arr)  

Here's the for loop to get the sum of diagonal and antidiagonal elements of an arrray which are stored in two variables 'diag' and 'antidiag'.

for(i=0;i<n;i++)
{
    diag+=arr[i][i];
    antidiag+=arr[i][(n-1)-i];
}

Then we store its absolute difference in a variable 'sum' using the function 'abs()'.

sum=abs(diag-antidiag);

Here's the entire function 'diagonalDifference'.

int diagonalDifference(vector<vector<int>> arr) 
{
    int n=arr.size(),diag=0,antidiag=0,sum=0,i;
    for(i=0;i<n;i++)
    {
        diag+=arr[i][i];
        antidiag+=arr[i][(n-1)-i];
    }
    sum=abs(diag-antidiag);
    return sum;
}

In the main function we basically take in array elements and then pass it to our 'diaginalDifference' function and store it in a variable 'result'

You can also solve the problem with or without using vector. But since in HackerRank the problem is to be solved with vector, here's the solution for that.

For doing it without vector array, the logic behind remains the same but things like storage, calculation process, time complexity etc changes

Here's the complete program

int diagonalDifference(vector<vector<int>> arr) 
{
    int n=arr.size(),diag=0,antidiag=0,sum=0,i;
    for(i=0;i<n;i++)
    {
        diag+=arr[i][i];
        antidiag+=arr[i][(n-1)-i];
    }
    sum=abs(diag-antidiag);
    return sum;
}

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

    string n_temp;
    getline(cin, n_temp);

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

    vector<vector<int>> arr(n);

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

        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 < n; j++) {
            int arr_row_item = stoi(arr_row_temp[j]);

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

    int result = diagonalDifference(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;
}