c++ set vector size at initialization code example

Example 1: c++ initialize size of 3d vector

vector<vector<vector<double>>> f(3, vector<vector<double>>(4, vector<double>(5)));

Example 2: c++ create vector of size

// create a vector with 20 integer elements
std::vector<int> arr(20);

for(int x = 0; x < 20; ++x)
   arr[x] = x;

Example 3: c++ vector initialize size

vector<Entry> array(1000);//size of 1000