C++ : 배열eotls modern C++ std::vector 사용하기

 

1. GridCell.cpp 파일을 추가한다.

#pragma once

class Cell {
public:
	Cell(double value): m_value(value) {}
	~Cell(){};

	void SetValue(double value);
	double GetValue() const;

private:
	double m_value;
};

class GridCell
{
public:
	GridCell(int rows, int columns): m_rows(rows), m_columns(columns), m_cells(nullptr){
		m_rows = rows;
		m_columns = columns;

		m_cells = new double*[m_rows];
		for (int i = 0; i < m_rows; ++i) {
			m_cells[i] = new double[m_columns]();
		}
	}
	~GridCell() {
		for (int i = 0; i < m_rows; ++i) {
			delete[] m_cells[i];
		}
		delete[] m_cells;
	}

	void SetCell(int row, int column, double value) {
		if (row >= m_rows || column >= m_columns) {
			return;
		}
		m_cells[row][column] = value;
	}
	double GetCell(int row, int column) const {
		if (row >= m_rows || column >= m_columns) {
			return 0.0;
		}
		return m_cells[row][column];
	}
	void SetSize(int rows, int columns) {
		m_rows = rows;
		m_columns = columns;	
	}

private:
	int m_rows;
	int m_columns;	
	double** m_cells;
};

 

2. 메모리 누수 방지를 위해 modern C++  std::vector를 사용합니다.

#pragma once

#include <vector>

class Cell {
public:
    Cell(double value) : m_value(value) {}
    ~Cell() = default;

    void SetValue(double value) {
        m_value = value;
    }

    double GetValue() const {
        return m_value;
    }

private:
    double m_value;
};

class GridCell
{
public:
    GridCell(int rows, int columns)
        : m_rows(rows),
        m_columns(columns),
        m_cells(rows, std::vector<double>(columns, 0.0))
    {
    }

    ~GridCell() = default;

    void SetCell(int row, int column, double value) {
        if (row < 0 || row >= m_rows ||
            column < 0 || column >= m_columns) {
            return;
        }

        m_cells[row][column] = value;
    }

    double GetCell(int row, int column) const {
        if (row < 0 || row >= m_rows ||
            column < 0 || column >= m_columns) {
            return 0.0;
        }

        return m_cells[row][column];
    }

    void SetSize(int rows, int columns) {
        m_rows = rows;
        m_columns = columns;

        m_cells.resize(rows);

        for (auto& rowVec : m_cells) {
            rowVec.resize(columns, 0.0);
        }
    }

private:
    int m_rows;
    int m_columns;

    std::vector<std::vector<double>> m_cells;
};

 

3. 다음도 참고하세요.

int rows = 4;
int columns = 3;

std::vector<std::vector<double>> cells(rows, std::vector<double>(columns, 0.0));
        
또는
        
std::vector<std::vector<double>> cells{std::vector<std::vector<double>>(rows, std::vector<double>(columns, 0.0))};

 

4. 컴파일 시점에 크기를 결정하는 std::array도 참고하세요.

#include <array>

std::array<std::array<double, 3>, 4> cells{};
cells[1][2] = 3.14;
double value = cells[1][2];

for(const auto& row : cells) {
	for (double value : row) {
		std::cout << value << " ";
	}
	std::cout << std::endl;
}