Error shows as “Expression must have a const value” when integer variable is used for declaring array size in c++

Question

Hi i have below code ,

# include <iostream>
# include <limits>

using namespace std;

int main()
{
    int runs,innings,timesnotout,n;
    cout<<"Enter the number of players:";
    cin>>n;
    const char name[n][10]; //here error shows as "Expression must have a  constant value" is displayed


}

i am trying to get n value from input and then using the n value as array size

Answer 1

This means exactly what the error message says. You may only use constant expressions declaring arrays. In your case it would be better to use either std::vector<std::string> or even std::vector<std::array<char, 10>>` or to allocate the array in the heap.

Answer 2

If you intend to keep the statistics per player, you should define a struct/class and a vector of such:

struct PlayerStats
{
    std::string Name;
    unsigned int Runs;
    unsigned int Innings;
    unsigned int TimesNotOut;
};

int main()
{
    unsigned int n = 0;
    std::cout << "Enter number of players:  ";
    std::cin >> n; // some error checking should be added
    std::vector<PlayerStats> players(n);
    // ... etc
    return 0;
}

Answer 3

When you want to store something without knowing beforehand the size, you can use a vector. Because it can grow dynamically during the execution of your program.

In your case, you can use something like:

#include <iostream>
#include <vector>

using namespace std;

int main() {

   std::vector<string> nameVec;

   nameVec.push_back("John");
   nameVec.push_back("Kurt");
   nameVec.push_back("Brad");
   //Warning: Sometimes is better to use iterators, because they are more general
   for(int p=0; p < nameVec.size(); p++) {
     std::cout << nameVec.at(p) << "\n";
   }

}