surface_area.cpp

/**
 * Madison, is a little girl who is fond of toys.
 * Her friend Mason works in a toy manufacturing factory.
 * Mason has a 2D board A of size H x W with H rows and W columns.
 * The board is divided into cells of size 1 x 1 with each cell indicated
 * by it's coordinate (i, j). The cell (i, j) has an integer A_ij written on it.
 * To create the toy Mason stacks A_ij number of cubes of size 1 x 1 x 1 on the
 * cell (i, j). Given the description of the board showing the values of A_ij
 * and that the price of the toy is equal to the 3D surface area find the price
 * of the toy.
 */

#include "surface_area.hpp"

#include <cstdlib>

using namespace std;

long long surface_area(const std::vector<std::vector<int>>& figure) {
    if (figure.empty() || figure[0].empty()) {
        return 0;
    }
    size_t n = figure.size(), m = figure[0].size();
    long long area = 2 * n * m;
    for (size_t i = 0; i < n; ++i) {
        area += figure[i][0];
    }
    for (size_t i = 0; i < n; ++i) {
        area += figure[i][m - 1];
    }
    for (size_t j = 0; j < m; ++j) {
        area += figure[0][j];
    }
    for (size_t j = 0; j < m; ++j) {
        area += figure[n - 1][j];
    }
    for (size_t i = 0; i < n; ++i) {
        for (size_t j = 1; j < m; ++j) {
            area += abs(figure[i][j] - figure[i][j - 1]);
        }
    }
    for (size_t j = 0; j < m; ++j) {
        for (size_t i = 1; i < n; ++i) {
            area += abs(figure[i][j] - figure[i - 1][j]);
        }
    }
    return area;
}