Cofactor Matrix

Problem

Compute the 3x3 cofactor matrix C of a 3x3 matrix A.

C[i][j] = (-1)^(i+j) * det(minor(A, i, j)), where the minor deletes row i and column j.

Hint

Signs alternate like a checkerboard starting with + at (0, 0).

case 1

in: [[[1,0,0],[0,1,0],[0,0,1]]]

expected: [[1,0,0],[0,1,0],[0,0,1]]

case 2

in: [[[1,2,3],[4,5,6],[7,8,9]]]

expected: [[-3,6,-3],[6,-12,6],[-3,6,-3]]

case 3

in: [[[2,0,0],[0,3,0],[0,0,4]]]

expected: [[12,0,0],[0,8,0],[0,0,6]]

case 4

in: [[[1,2,3],[0,1,4],[5,6,0]]]

expected: [[-24,20,-5],[18,-15,4],[5,-4,1]]

Starter codePython

def cofactor_matrix(A):
    # Your code here
    pass

4 test cases · run your code against them in the editor