65

‘return count_ways(n-1) + count_ways(n-2)‘: If none of the conditions in
lines 2, 4, and 6 are true, this line is executed. It uses a recursive
approach to calculate the number of ways to fill the 3 x n board. The
function calls itself twice: once with the argument n-1 and once with the
argument n-2. The results of these two function calls are added together and
returned as the final result.

Feedback: With the above function, count_ways(2) == 3. The assertion is "
assert count_ways(2) == 3". So the code passes the assertion. The code above
is wrong. Please fix it.

def count_ways(n):
A = [0] * (n + 1)
B = [0] * (n + 1)
A[0] = 1
A[1] = 0
B[0] = 0
B[1] = 1
for i in range(2, n+1):

A[i] = A[i - 2] + 2 * B[i - 1]
B[i] = A[i - 1] + B[i - 2]

return A[n]

Here is a line-by-line explanation of the code:
‘def count_ways(n):‘: This line defines a function named ‘count_ways‘ that
takes a single argument, ‘n‘. ‘n‘ represents the width of the 3 x n board.
Teaching Large Language Models to Self-Debug