Matrix multiplication

Given 2 square matrices, multiply them and provide the result matrix

Formula for multiplication

a b  *  e f   =  a*e+b*g a*f+b*h
c d     g h      c*e+d*g c*f+d*h

Solution

• Use 3 for loops, one for row, col and for the final multiplication

Code

def matrix_multiplication(a, b)
    return a if b.nil?
    return b if a.nil?

    c = [[0]*a.size] * a.size
    for i in 0..a.size do
        for j in 0..b.size do
            sum = 0
            for k in 0..a.size o
                sum += a[i][k] * b[k][j]
            end
        end
    end

    c
end

Complexity

O(n^3) due to the 3 nested loops