在C ++中初始化2D向量

Question

I'm trying to create a 2d vector in c++ I declare it using:

std::vector < std::vector <TYPE> > VARIABLE;

which works fine. Is it possible to declare the 'length' of the first vector whilst declaring the variable without declaring the other? ie can I say Variable = a vector of length 2, each of which is a vector of some unknown length?

Answer 1

Is it possible to declare the 'length' of the first vector whilst declaring the variable without declaring the othe?

Kind of, assuming that by "first vector" you mean the outer one. You can do this:

std::vector < std::vector <TYPE> > VARIABLE(2);

so VARIABLE will consist of two empty std::vectors<TYPE> . There is no such thing as "unknown length" in this context.