从1楼到2楼有h级台阶，某同学上楼的习惯是一次上1级或2级，写一算法输出该同学上这h级台阶时的所有不同的上法，用回溯法实现，开辟堆栈保存上楼方法(From the 1 floor to the 2 floor H steps, a classmate upstairs is a habit of 1 or 2, write an algorithm to the output of the students on the H level of all the different method, using backtracking to achieve open, save up stack method)