2.06 Algorithm Basics

2.6 Algorithm Basics (REVISED) Curriculum Page

Answer the following questions with your POGIL team:

1. For the robot in the maze above, is CAN_MOVE(forward) true? Is CAN_MOVE(right) true?

For the robot, CAN_MOVE(forward) is true, however CAN_MOVE(right) is not true.

1. (Portfolio) Write an algorithm using the 4 commands above to navigate the robot through the maze to reach the gray square. You can pretend that one of you is the robot and walk through your algorithm with your fingers on the maze. Are there commands that are repeated in your algorithm? Circle them.

MOVE_FORWARD

MOVE_FORWARD

ROTATE_RIGHT

MOVE_FORWARD

MOVE_FORWARD

MOVE_FORWARD

MOVE_FORWARD

ROTATE_LEFT

MOVE_FORWARD

MOVE_FORWARD

3.)(Portfolio) Let's replace the repeated commands with a repetition control structure. The following command can be used to repeat a block of commands:

REPEAT n times

Commands

Rewrite your algorithm above using Repeat n times control structures (substituting in a

number for n) instead of repeating the MOVE_FORWARD command many times.

if(CAN_MOVE(forward) = true)

REPEAT 2 times

if(CAN_MOVE(right) = true)

ROTATE_RIGHT

if(CAN_MOVE(forward) = true)

REPEAT 4 times

if(CAN_MOVE(left) = true)

ROTATE_LEFT

if(CAN_MOVE(forward) = true)

REPEAT 2 times

4.) Can you come up with a more general algorithm to navigate a maze using IF commands and a REPEAT UNTIL GoalReached command, which tests if the robot has reached the gray square goal? Try to come up with an algorithm before looking at the algorithm on the next page.

REPEAT UNTIL GoalReached

{

if(CAN_MOVE(forward) = true)

MOVE_FORWARD

if(CAN_MOVE(right) = true)

ROTATE_RIGHT

if(CAN_MOVE(left) = true)

ROTATE_LEFT

}

Here’s a more general way to navigate a maze with the following algorithm which uses GoalReached to test if the robot has reached the gray square.

REPEAT UNTIL GoalReached

{

IF (CAN_MOVE forward)

MOVE_FORWARD

IF (CAN_MOVE left)

ROTATE_LEFT

IF (CAN_MOVE right)

ROTATE_RIGHT

}

1. Which part(s) of the algorithm above are selection control structures? Highlight them.
2. Which part of the algorithm above is a repetition control structure? Circle it. Remember a control structure can consist of multiple statements. Any of the IF(CAN) would be a repetition control structure. Along with the REPEAT UNTIL goalreached

1. Does the algorithm solve the maze above and navigate the robot to the goal, the gray square? How many times does it need to run through the loop? Yes, it would navigate the robot through the maze. It must be played 10 times.

1. (Portfolio) Can you come up with a maze that this algorithm will not be able to solve? Describe or take a photo of your drawing of such a maze for your portfolio.

If a maze had something with more than one true statement, such as a loop where the algorithm could turn either left or right, then the algorithm could not complete the maze because it would constantly be turning right, or whichever direction appeared first in the algorithm.

5.) (Portfolio) Write an algorithm for washing a stack of 10 items that are cups and saucers mixed together, where the rule is that the cups are washed in hot water and the saucers in cold water. Use simple commands like hot_wash and cold_wash. You may also use the control structures IF and REPEAT n times. Identify the parts of your algorithm that are examples of Sequence, Selection, and Repetition.

REPEAT 10 TIMES {

IF (is_cup)

hot_wash

ElSE

cold_wash

}

The REPEAT 10 TIMES is an example of repetition. The IF(is_cup) is selection and the code is a sequence