CPP

c++ vector resize

std::vector<int> vec = {1, 2, 3};
vec.resize(2); // {1, 2}
vec.resize(4); // {1, 2, 0, 0,}
vec.resize(6, 9);  // {1, 2, 0, 0, 9, 9}

3d vector c++ resize

dp.resize(n+1,vector<vector<int>>(n+1,vector<int>(n+1,-1)));

Resize vector c++

resize (size_type n, const value_type& val);

The resize() method (and passing argument to constructor is equivalent to that)
  
will insert or delete appropriate number of elements to the vector to make it

given size (it has optional second argument to specify their value). 

when a vector in c++ is resized what happens to the elements of the vector

The C++ function std::vector::resize() changes the size of vector. If n is smaller than current size then extra elements are destroyed.

If n is greater than current container size then new elements are inserted at the end of vector.

If val is specified then new elements are initialed with val.