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  1. Prepare
  2. Mathematics
  3. Linear Algebra Foundations
  4. Linear Algebra Foundations #3- Matrix Multiplication
  5. Discussions

Linear Algebra Foundations #3- Matrix Multiplication

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9 Discussions

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  • amine_ifri
     + 0 comments

    Why is the platform not providing the INPUT/OUTPUT format they are looking for? Is the goal to test whether one can multiply a 2x2 matrix, or to test whether one knows how to parse INPUT data from commande line ?

    Be specific!

    if name == 'main': ## Read code fron STDIN n = 2 # Number of rows/columns matrix1 = [list(map(int, input().split())) for _ in range(n)] matrix2 = [list(map(int, input().split())) for _ in range(n)]

    # OR:
# matrix1 = [[1, 2], [2, 3]]
# matrix2 = [[4, 5], [7, 8]]

print("A = {0}".format(matrix1[0][0]*matrix2[0][0] + matrix1[0][1]*matrix2[1][0]))
print("B = {0}".format(matrix1[0][0]*matrix2[0][1] + matrix1[0][1]*matrix2[1][1]))
print("C = {0}".format(matrix1[1][0]*matrix2[0][0] + matrix1[1][1]*matrix2[1][0]))
print("D = {0}".format(matrix1[1][0]*matrix2[0][1] + matrix1[1][1]*matrix2[1][1]))

  • jachi334
     + 0 comments
    A = [[1,2],[2,3]]
B = [[4,5],[7,8]]

ROWS_A, COLS_A = len(A), len(A[0])
ROWS_B, COLS_B = len(B), len(B[0])
assert COLS_A == ROWS_B
COMMON_D = ROWS_B

# zeros for Rows-A x Cols-B
M_TIMES = []
for r in range(ROWS_A):
    M_TIMES.append( [0] * COLS_B )

# Loop over Rows-A, then Cols-B, then the common dimension
for rA in range(ROWS_A):
    for cB in range(COLS_B):
        for t in range(COMMON_D):
            M_TIMES[rA][cB] += A[rA][t]*B[t][cB]
        print(M_TIMES[rA][cB])

  • hoangziet22
     + 0 comments
    a = [1, 2], [2, 3]
b = [4, 5], [7, 8]
res = 0 
for i in range(2):
        for j in range(2):
                for k in range(2):
                        res += a[i][k]*b[k][j]           
                print(res)
                res = 0

  • chisom213
     + 1 comment

    Python3:

    # Enter your code here. Read input from STDIN. Print output to STDOUT
if __name__ == "__main__":
  matrix1 = [[1, 2], [2, 3]]
  matrix2 = [[4, 5], [7, 8]]
  elem = 0
  
  for i in range(len(matrix1)): # row in 1st matrix
    for j in range(len(matrix2[0])): # column in 2nd matrix
        for k in range(len(matrix2)): # position index
            elem += matrix1[i][k] * matrix2[k][j]
        print(elem)
        elem = 0

    or

    if __name__ == "__main__":
    M, N = [[1, 2], [2, 3]], [[4, 5], [7, 8]]
    
    lst = []
    for row1m in M:
        for j in range(len(row1m)-1):
            lst += [row1m[j]*N[0][0] + row1m[j+1]*N[1][0]]
            lst += [row1m[j]*N[0][1] + row1m[j+1]*N[1][1]]  
    print(*lst, sep='\n')

  • steph_andre
     + 0 comments
    a1 = [1,2]
a2 = [2,3]


matrix_a = [a1,a2]

b1 = [4,5]
b2 = [7,8]


matrix_b = [b1,b2]

c1 = [0, 0]
c2 = [0, 0]


matrix_c = [c1,c2]

for i in range(len(matrix_a)):
   for j in range(len(matrix_b[0])):
       for k in range(len(matrix_b)):
           matrix_c[i][j] += matrix_a[i][k] * matrix_b[k][j]

for n in range(len(matrix_c)):
  for i in range(len(matrix_c[n])):
    print(matrix_c[n][i])