CodeWars/4kyu/matrix_determinant/solution.cpp

#include <cmath>
#include <iostream>
#include <vector>

using namespace std;

vector<vector<long long>> transform(vector<vector<long long>> m, int row,
                                    int col) {
    vector<vector<long long>> result;

    for (int i = 0; i < m.size(); i++) {
        if (i == row)
            continue;
        vector<long long> actual_row;
        for (int j = 0; j < m[i].size(); j++) {
            if (j == col)
                continue;
            actual_row.push_back(m[i][j]);
        }
        result.push_back(actual_row);
    }

    return result;
}

long long determinant(vector<vector<long long>> m) {
    switch (m.size()) {
    case 1:
        return m[0][0];
        break;
    case 2:
        return m[0][0] * m[1][1] - m[0][1] * m[1][0];
        break;
    }

    long long result = 0;

    for (int i = 0; i < m.size(); i++) {
        auto l_m = transform(m, i, 0);
        result += pow(-1, i + 2) * m[i][0] * determinant(l_m);
    }

    return result;
}