如何用C++中的大小初始化3维向量

Question

For example, if we initialize vector<vector<vector<double>>> f , the dimension in each direction is not specified. So, I am wondering, what command should we insert to make f have size of [3][4][5] . Do we use new or something else?

Thanks for helping me out!

Answer 1

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

Answer 2

If you have already declared the vector and you want to initialize it, this is one way you can do it:

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

Answer 3

std::vector<std::vector<std::vector<double>>> f(3, std::vector<std::vector<double>>(4, std::vector<double>(5,0.0)));

For anyone who wants it without namespace std. Also the values in this f[3][4][5] are initialised to 0.0 which might be useful.