関連ワード:  how to get size of vector in c++    how to find size of vector in c++    how to get length of vector in c++    how to check size of vector in c++    how to calculate size of vector in c++    how to get size of 2d vector in c++    how to get size of vector array in c++    how to find length of vector in c++    how to check length of vector in c++    how to find size of vector matrix in c++