how to intialize vector in c++ with size and value code example

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

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

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;