# Lab 11: Array-Backed Grids¶

Part 1: 10 pts. Start with the program at the end of Array-Backed Grids. Modify it so that rather than just changing the block the user clicks on, also change the blocks of the squares next to the user’s click. If the user clicks on an edge, make sure the program doesn’t crash and still handles the click appropriately.

Part 2: 10 pts. Write a celebrity-finding function. Start with a function check_celebrity that takes an n by n matrix named grid as a parameter. The grid location grid[i][j] = 1 if person i knows person j and grid[i][j] = 0 otherwise. (Assume that grid[i][i] = 1 for every i, since every person knows him/herself.) A celebrity is a person who is known by everyone and does not know anyone besides him/herself. Write a function that given the matrix grid, prints all the celebrities.

For example, in the following grid person 2 is a celebrity:

In the next example no one is a celebrity:

     0  1  2  3  4
----------------
0 |  1  1  1  0  1
1 |  0  1  1  0  1
2 |  0  0  1  0  0
3 |  1  0  1  1  1
4 |  1  0  0  1  1


Remember: A matrix can be represented as a list-of-lists, where each sub-list is a row of the matrix. For example, the first matrix can be represented as:

grid = [ [1, 1, 1, 0], [0, 1, 1, 0], [0, 0, 1, 0], [1, 0, 1, 1] ]


Or you can use multiple lines to define the grid:

grid = [ [1, 1, 1, 0],
[0, 1, 1, 0],
[0, 0, 1, 0],
[1, 0, 1, 1] ]


You can test your function with code like the following test cases:

# Put your "check_celebrity" function below this line

# The code will test your function

print("Test 1, Should show #2 is a celebrity.")
grid = [ [1, 1, 1, 0],
[0, 1, 1, 0],
[0, 0, 1, 0],
[1, 0, 1, 1] ]

check_celebrity(grid)

print("Test 2, Should show no one is a celebrity.")
grid = [ [1, 1, 1, 0, 1],
[0, 1, 1, 0, 1],
[0, 0, 1, 0, 0],
[1, 0, 0, 1, 1],
[1, 0, 0, 1, 1] ]

check_celebrity(grid)

print("Test 3, Should show #2 is a celebrity.")
grid = [ [1, 1, 1, 0, 1],
[0, 1, 1, 0, 1],
[0, 0, 1, 0, 0],
[0, 0, 1, 0, 1],
[1, 0, 1, 1, 1] ]

check_celebrity(grid)

print("Test 4, Should show no one is a celebrity.")
grid = [ [1, 1, 1, 0, 1],
[0, 1, 1, 0, 1],
[1, 0, 1, 0, 0],
[0, 0, 1, 0, 1],
[1, 0, 1, 1, 1] ]

check_celebrity(grid)
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