Create determinant_calculator.py

Author: Naman-Vasudev

matrix/determinant_calculator.py

@@ -0,0 +1,70 @@
+# Wikipedia URL- https://en.wikipedia.org/wiki/Determinant
+
+def get_minor(matrix: list[list[int] | list[float]], row: int, col: int) -> list[list[int] | list[float]]:
+    """
+    Returns the minor matrix obtained by removing the specified row and column.
+
+    Parameters
+    ----------
+    matrix : list[list[int] | list[float]]
+        The original square matrix.
+    row : int
+        The row to remove.
+    col : int
+        The column to remove.
+
+    Returns
+    -------
+    list[list[int] | list[float]]
+        Minor matrix.
+    """
+    return [r[:col] + r[col+1:] for i, r in enumerate(matrix) if i != row]
+
+
+def determinant_manual(matrix: list[list[int] | list[float]]) -> int | float:
+    """
+    Calculates the determinant of a square matrix using cofactor expansion.
+
+    Parameters
+    ----------
+    matrix : list[list[int] | list[float]]
+        A square matrix.
+
+    Returns
+    -------
+    int | float
+        Determinant of the matrix.
+
+    Examples
+    --------
+    >>> determinant_manual([[1,2],[3,4]])
+    -2
+    >>> determinant_manual([[2]])
+    2
+    >>> determinant_manual([[1,2,3],[4,5,6],[7,8,9]])
+    0
+    """
+    n = len(matrix)
+
+    if n == 1:
+        return matrix[0][0]
+
+    if n == 2:
+        return matrix[0][0]*matrix[1][1] - matrix[0][1]*matrix[1][0]
+
+    det = 0
+    for j in range(n):
+        minor = get_minor(matrix, 0, j)
+        cofactor = (-1) ** j * determinant_manual(minor)
+        det += matrix[0][j] * cofactor
+    return det
+
+
+if __name__ == "__main__":
+    # Simple demo
+    matrix_demo = [
+        [1, 2, 3],
+        [4, 5, 6],
+        [7, 8, 9]
+    ]
+    print(f"The determinant is: {determinant_manual(matrix_demo)}")