TA SURVEY Have the TA write their name on the board Fill out the survey at: The TA should walk out 5 minutes MAX  Still have a lot to do today!!

CMSC 201 MR. LUPOLI Problem Solving

Steps to Solve a Problem Read the problem completely many times. Solve the problem manually with a few sets of sample data. (or smaller pieces!!) Optimize the manual steps. Write the manual steps as comments or pseudo- code. Add to the comments or pseudo-code with real code. Optimize the real code.

Read the problem. Do not assume anything! Make sure to view the demonstration as well (if given) Instructions  Create directory lab12  Move to that directory and copy a file already created for you. cp /afs/umbc.edu/users/s/l/slupoli/pub/labCode201/lab12.py.

Reading the Problem Visit: Read the problem In lab12.py  Describe the project you are about to start in the file header “description”

Reading the Problem Under your description of the project, within comments, list your questions ''' 1. When is this project due? 2. Will the grid always be 20 x 20? 3. Will each number be an integer? '''

Reading the Problem Why am I typing this inside the file?  Used a Comment  Can copy and paste to an to my TA/instructor  Can add the answer later  A reminder

Using sample data Can we downsize the problem slightly  Usually we can, now more manageable  Make sure it has valid data and really tests your application  A new matrix of all 1’s is useless!!! We will make a 5 x 5 matrix instead Grab some paper and draw this test matrix out!!  Can still manually solve  What would the largest value be for HORIZONTAL and VERTICAL?

Using sample Data In main, a 5 by 5 matrix named “twoD” has been created for you!!  Fill the rest of the matrix with values (not done for you) # setup twoD = [0] * ROWS for i in range(ROWS): twoD[i] = [0] * COLS # enter 25 values individually twoD[0][0] = 4

Solve the problem Let’s break it down first Easy one first  Multiply horizontally  twoD[0][0] * twoD[0][1] * twoD[0][2] * twoD[0][3]  Store value  Compare with maximum value so far  Then twoD[0][1] * twoD[0][2] * twoD[0][3] * twoD[0][4]  Store value  Compare with maximum value so far  … (in a loop)

Solving the problem In thinking it out, what do we have to watch out for??  Initializing a MAX value  Out of bounds  Comparison of the recently multiplied to the CURRENT MAX  Storing the NEW max value

Solving the Problem In your lab12.py  The function “multiplyHorizontal()” has been started  Will accept the matrix  Function will return the MAX value it determined  FYI - You will create multiplyVertical() AFTER you are successful with multiplyHorizontal()

Write the manual steps as comments Inside your new function  Comment on how you are going to solve it, step by step  Remember, you will need a nested loop, since we are dealing with a matrix  Similar to this: for i in range(ROWS-??): for j in range(COLS-??): answer = …

Add code to the comments Begin coding AFTER NEXT slide!!  On your own!! When you think you are done with THAT function  Call the function from main(), while passing your test function # test matrix here maxHorizontal = multiplyHorizontal(twoD) print(maxHorizontal) Make sure your result is correct Move onto multiplyVertical( )

What to show your TA Questions about the project inside lab12.py Drawn test matrix Coded  TEST matrix  COMPLETED multiplyHorizontal function  COMPLETED multiplyVertical function Running Code  PRINTED AND CORRECT value from multiplyHorizontal and multiplyVertical function