Dot Product of Matrix Columns

Problem

Compute the dot product of columns i and j of a matrix A.

Sum the products of paired entries down the two columns. When i = j this returns the squared norm of that column.

Hint

Walk down the rows and accumulate row[i] * row[j].

case 1

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

expected: 14

case 2

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

expected: 10

case 3

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

expected: 0

case 4

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

expected: 44

Starter codePython

def matrix_columns_dot(A, i, j):
    # Your code here
    pass

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