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Fix minor typo and add matrix dimension check #6367

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Sep 24, 2022
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9 changes: 8 additions & 1 deletion matrix/inverse_of_matrix.py
Original file line number Diff line number Diff line change
Expand Up @@ -27,14 +27,21 @@ def inverse_of_matrix(matrix: list[list[float]]) -> list[list[float]]:
[[0.25, -0.5], [-0.3, 1.0]]
"""

D = Decimal # An abbreviation to be conciseness
D = Decimal # An abbreviation for conciseness

# Check if the provided matrix has 2 rows and 2 columns, since this implementation only works for 2x2 matrices
if len(matrix) != 2 or len(matrix[0]) != 2 or len(matrix[1]) != 2:
raise ValueError("Please provide a matrix of size 2x2.")

# Calculate the determinant of the matrix
determinant = D(matrix[0][0]) * D(matrix[1][1]) - D(matrix[1][0]) * D(matrix[0][1])
if determinant == 0:
raise ValueError("This matrix has no inverse.")

# Creates a copy of the matrix with swapped positions of the elements
swapped_matrix = [[0.0, 0.0], [0.0, 0.0]]
swapped_matrix[0][0], swapped_matrix[1][1] = matrix[1][1], matrix[0][0]
swapped_matrix[1][0], swapped_matrix[0][1] = -matrix[1][0], -matrix[0][1]

# Calculate the inverse of the matrix
return [[float(D(n) / determinant) or 0.0 for n in row] for row in swapped_matrix]