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The std::vector lives in the <vector> header. So first, we need to add this line of code at the top of the program:

#include <vector>

For review, #include is a preprocessor directive that tells the compiler to include whatever library that follows. In our case that is the standard vector library.

And the syntax to create a vector looks like:

std::vector<type> name;

So to define a vector of ints called calories_today:

std::vector<int> calories_today;

Inside the angle brackets is the data type of the vector. After the angle brackets is the name of the vector.

Note: The type of the vector (i.e., what data type is stored inside) cannot be changed after the declaration.



The Tokyo Subway has different payment options for adults and children. We have declared a double vector already named subway_adult.

Declare another double vector named subway_child.

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