## Backtracking – 1000 locks and 1000 students problem

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony: I’m sure I’ll write a lot more interesting things in the future. There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it....