Size of array of vectors of different sizes cpp

Question

I have a function which accepts array of vectors of different sizes I want to know how many vectors are present in array

int dfs(vector<int> g[])
{
   int n=?;//(no. of vector in array)
}

You cannot, pass in the size separately or use a top level `vector`. — Tanveer Badar, Feb 11 '20 at 02:13
I am solving a functional problem and this is what i am getting as parameter which cannot be changed — Atharwa Adawdakar, Feb 11 '20 at 02:15
Unfortunately, C++ does not work this way. This cannot be done in C++. — Sam Varshavchik, Feb 11 '20 at 02:18

score 3 · Accepted Answer · answered Feb 11 '20 at 02:20

There is no way to do this in C++: an array type in a function parameter decays to a pointer, which has no size information.

The best option is to take the parameter as a std::vector<std::vector<int>>, but you mention in a comment that that is not possible.

One other option, if you are sure you will be passed an array (in comparison to a pointer to an array) is to change the definition to something like this:

template <std::size_t n>
int dfs(std::vector<int>(&g)[n]) {
  // n is the number of elements in the array
}

Size of array of vectors of different sizes cpp

1 Answers1