递归模板

def recursion(level, param1,param2, ...):
    #recursion terminator
    if level >MAX_LEVEL:
        print_result
        return

    #process logic in current level
    process_data(level, data...)

    #drill down
    self.recursion(level+1,p1, ...)

    #reverse the current level status if needed
    rverse_state(level)