size of vector c++ initialization code example

Example 1: c++ initialize vector of vector with size

vector<vector<int>> v(10, vector<int>(10));

Example 2: c++ initialize size of 3d vector

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

Example 3: declare vector of size n in c++

#include <vector>

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