The Lock class of the preceding problem has a small problem. It does not support combinations that start with one or more zeroes. For example, a combination of $0042$ can be opened by entering just $42.$

Solve this problem by choosing a different representation. Instead of an integer, use a string to hold the input.

Once again, the configuration is hardwired. You will see in Section $8\mathrm{.}6$ how to change it$.$