p = max(m, n)
if m < p:
left-pad A's shape with 1s until it also has p dimensions
else if n < p:
left-pad B's shape with 1s until it also has p dimensions
result_dims = new list with p elements
for i in p-1 ... 0:
A_dim_i = A.shape[i]
B_dim_i = B.shape[i]
if A_dim_i != 1 and B_dim_i != 1 and A_dim_i != B_dim_i:
raise ValueError("could not broadcast")
else:
# Pick the Array which is having maximum Dimension
result_dims[i] = max(A_dim_i, B_dim_i)