3d vector c 2b 2b resize

1dp.resize(n+1,vector<vector<int>>(n+1,vector<int>(n+1,-1)));
2

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

1resize (size_type n, const value_type& val);
2
3The resize() method (and passing argument to constructor is equivalent to that)
4  
5will insert or delete appropriate number of elements to the vector to make it
6
7given size (it has optional second argument to specify their value).