9. 2D Lists

9.1. Before Kattis

Before you do ANYTHING, take out a scrap piece of paper.

Note, do not work on the assignments during labs. If you do, you will be asked to leave and will be given a zero for the lab.

Let’s say we have this code:

twoD = [['a', 'b', 'c'],
        ['d', 'e', 'f'],
        ['g', 'h', 'i']]

Warning

Above is a 3x3 matrix. YOUR CODE SHOULD WORK ON ANY SIZED MATRIX THOUGH. 4x4, 5x23, 23098x198272973!!!

Long story short, this is bad; do not do this:

def printRow(mat, row):
   print(mat[row][0])
   print(mat[row][1])
   print(mat[row][2])

1

Write a function printRow(mat, row) that will print out all the contents in a 2D matrix mat from a given row row.

ex:

>>> printRow(twoD, 1)
d
e
f

2

Write a function printCol(mat, col) that will print out all the contents in a 2D matrix mat from a given col col.

ex:

>>> printCol(twoD, 2)
c
f
i

3

Write a function printDownRight(mat) that will print out all the contents in a 2D matrix mat along the diagonal starting at the top left and ending at the bottom right.

ex:

>>> printDownRight(twoD)
a
e
i

4

Write a function printUpRight(mat) that will print out all the contents in a 2D matrix mat along the diagonal starting at the bottom right and ending at the top right.

ex:

>>> printUpRight(twoD)
g
e
c

5

Write a function printDownLeft(mat) that will work similarly to above, but starting in the top right.

6

Write a function printUpLeft(mat) that will work similarly to above, but starting in the bottom right.

7

What happens if you were to use this list now?

uhoh = [['a', 'b', 'c', 'w'],
        ['d', 'e', 'f', 'x'],
        ['g', 'h', 'i', 'y'],
        ['j', 'k', 'l', 'z']]

All of your functions should still work as expected (see example below). If they do not, FIX THEM!!!!

>>> printCol(uhoh, 2)
c
f
i
l

>>> printUpRight(uhoh)
j
h
f
w

9.2. Kattis Problems

Grab a scrap piece of paper to start scratching your ideas down on paper. The problems are getting tricky enough where this really is becoming a requirement.

If you finish the lab, go back and work on incomplete problems from previous labs.

If you have somehow finished everything so far, go check out LeetCode. Sort the problems by Acceptance (click the table header) and start seeing if you can solve some of these problems.