How Can I Optimize the Initialization of a 2D std::vector in C ?

Optimal Initialization of a Two-Dimensional std::vector

Initializing multidimensional std::vectors presents certain challenges, particularly when aiming for efficient code. Consider the given example:

std::vector<std::vector<int>> fog;
for (int i = 0; i < A_NUMBER; i++) {
    std::vector<int> fogRow;
    for (int j = 0; j < OTHER_NUMBER; j++) {
        fogRow.push_back(0);
    }
    fog.push_back(fogRow);
}

This approach requires multiple nested loops and appears somewhat tedious. A more optimal solution exists using the std::vector::vector(count, value) constructor:

std::vector<std::vector<int>> fog(
    ROW_COUNT,
    std::vector<int>(COLUMN_COUNT)); // Defaults to zero initial value

In this case, the constructor takes an initial size and a default value. If a different default value is desired, it can be specified as follows:

std::vector<std::vector<int>> fog(
    ROW_COUNT,
    std::vector<int>(COLUMN_COUNT, 4));

Furthermore, utilizing uniform initialization introduced in C 11 provides a concise and readable method for vector initialization:

std::vector<std::vector<int>> fog { { 1, 1, 1 },
                                    { 2, 2, 2 } };

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