Std::bad alloc

This error is hard to solve and it may appear in many cases, so improve the article by adding as many cases as possible.

1. The solution for this problem is specific to each implementation, but there are some common mistakes to avoid. For example, the elements of a vector must be filled with the pointers, not the objects themselves. Detailed solution manual about this error message will be given later.
2. Avoid exceeding arrays. Don't do this:

     int *x;
     int a = 0,b = 0,c =0;
     x = new int[1];
     x[0] = a;
     x[1] = b;
     x[2] = c;
This code works, but if you continue to allocate memory, you may encounter this error message in the future.