在C++中迭代大小可变的N维矩阵

#include <iostream>
#include <vector>

class DynamicMatrix {
public:
    DynamicMatrix(size_t rows, size_t cols) : data(rows, std::vector<int>(cols)) {}

    int& operator()(size_t row, size_t col) {
        return data[row][col];
    }

    const int& operator()(size_t row, size_t col) const {
        return data[row][col];
    }

    void resize(size_t new_rows, size_t new_cols) {
        data.resize(new_rows);
        for (auto& row : data) {
            row.resize(new_cols);
        }
    }

private:
    std::vector<std::vector<int>> data;
};

int main() {
    DynamicMatrix mat(3, 3);
    mat(0, 0) = 1;
    mat(1, 1) = 2;
    mat(2, 2) = 3;

    std::cout << "Matrix before resize:\n";
    for (size_t i = 0; i < 3; ++i) {
        for (size_t j = 0; j < 3; ++j) {
            std::cout << mat(i, j) << " ";
        }
        std::cout << "\n";
    }

    mat.resize(4, 4);
    std::cout << "Matrix after resize:\n";
    for (size_t i = 0; i < 4; ++i) {
        for (size_t j = 0; j < 4; ++j) {
            std::cout << mat(i, j) << " ";
        }
        std::cout << "\n";
    }

    return 0;
}