What\'s the Most Efficient Way to Initialize a 2D std::vector in C ?

Initializing Two-Dimensional std::vectors Efficiently

Consider the following code snippet:

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 method of initializing a two-dimensional std::vector appears inefficient. An alternative approach leveraging the std::vector::vector(count, value) constructor is available:

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

If a default value other than zero is desired, specify it as shown below:

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

Additionally, uniform initialization introduced in C 11 allows for concise initialization using {}:

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

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