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 Towers Of Hanoi
Tower Of Hanoi

 This KLA is transcribed from the SIGCSE 2004 Special Session on KLAs.

Overview To KLA

 Authors: Joanne Houlahan, Michael Sisk, Linda Lahti, and Leland Beck

 Summary: To understand and appreciate the necessity and beauty of recursion

 Course And Level: The KLA is appropriate for CS1-late.

 Class Size: This KLA is appropriate for any class size larger than 10.

 Preparation Time: No preparation time is required.

 Execution Time: This exercise should take between 5-15 minutes.

Planning For KLA

 Materials: The only objects needed are the students.

 Preparation: Minimal preparation is necessary. They must simply know the story of the towers.

Execution Of KLA

 Description: Select 4 or 5 student "disks" to come to the front of the room. Denote the left, right and middle slots. Get the student's names, and arrange them in order by their height (shortest at the front of the line on the right and the tallest at the back of the line on the left). Explain that no "up staging" is ever allowed, and only 1 student can move at a time. The goal is to line them all up on the right with the least number of moves (optional; have extra student count the number of moves). Have the seated students tell our "disks" where to move. Point out recursive cases as they happen (ie, if there are 5 total, and 3 get moved, point out they solved the 3 problem). Applause when done.

 Variants And Extra Topics: below

 • Building Up: Begin with 3 students first, then go to 5 or 6.
 • Code: Show real code version.

Constraints On KLA

 • Limited Vision: (including color-blindness)
 • Limited Hearing: one, few and many
 • Limited Mobility: one, few and many
 • Trouble Speaking: one, few and many
 • Touch Aversion: (including cultural) one, few and many
 • Other:

Pitfalls Of KLA

 Need varying heights and sufficient space in front of room.

Feedback And Use Notes