Creating arrays with the upper limit of 10^7

After checking out a few programs on codechef and geeksforgeeks, I have found that a lot of questions require arrays with bounds similar to 1 <= N <= 10^7(arr[1] to arr[10000000]). What should I do in such situations?

you can’t create a integer array for such a big number but you can create bitset upto 1e7

What is a bitset? I’m a noob at programming you see.

Bitset is a c++ stl library, which allow you to create an array of bits (only contain 0/1) of size up to 1e7