C++ code to find out the sum of the special matrix elements

Suppose, we are given a square matrix of dimensions n * n. The following values of the matrix are called special elements −

• Values that are in the main diagonal.

• Values that are in the second diagonal.

• Values of the row that has exactly (n - 1 / 2) rows above it and the same number of rows below it.

• Values of the column that has exactly (n - 1 / 2) columns at its left and right.

We find out the sum of these special values in the matrix.

So, if the input is like n = 4, mat = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, {13, 14, 15, 16}}, then the output will be 107.

Steps

To solve this, we will follow these steps −

res := 0 for initialize i := 0, when i < n, update (increase i by 1), do:    for initialize j := 0, when j < n, update (increase j by 1), do:    if i is same as j or i is same as n / 2 or j is same as n/ 2 or i + j is same as n - 1, then:       res := res + mat[i, j] print(res)

Example

Let us see the following implementation to get better understanding

#include <bits/stdc++.h> using namespace std; #define N 100 void solve(int n, vector<vector<int>> mat) {    int res = 0;    for (int i = 0; i < n; i++)    for (int j = 0; j < n; j++){       if (i == j || i == n / 2 || j == n / 2 || i + j == n - 1)          res += mat[i][j];    }    cout << res << endl; } int main() {    int n = 4;    vector<vector<int>> mat = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, {13, 14, 15, 16}};    solve(n, mat);    return 0; }

Input

4, {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, {13, 14, 15, 16}}

Output

107