Unit #3-05

Learning Outcome

At the end of this lesson, you will be able to:

• understand and use recursion

  • Magic Squares

Review

• what is a recursion

  • a function that calls itself

Lesson

• read "Functions", Chapter 3, Computer Based Problem Solving

  • read "Recursion"

Activity

• read over this on Magic Squares

• find out your magic number related to your birthday!

Daily Assignment

• magic squares are another great example of a problem that can be solved by using recursion

  • Problem: create a program that generates all the magic squares with a magical number equal to 15

    • this means all the integers from 1 to 9

    • the easiest way to do this internally is to save the magic square in a 1 dimensional array of size 9 (ex [2,7,6,9,5,1,4,3,8])

  • before you start anything, ensure you have a design:

    • this might help: http://www.math.colostate.edu/~betten/courses/M152/LECTURE/lecture9.html

• create a flowchart for:

  • a function that accepts an array that is the magic square and returns whether it is a magic square or not (if it is not a valid 9 element array, automatically return False)

    • to be magic all the rows, columns and diagonals must all be equal.

    • as soon as this is not true, return false

• create a  second flowchart for:

  • a recursive function that generates 3x3 magic squares using only the numbers 1 to 9

    • you will need your function above!

• this starter repo might help

  • GitHub repo

Extra

• do the above in a second language