Lab 10 :Matrix Multiplication

[TOC]

Problem statement

Write a Python Program to implement Matrix Multiplication

Sample Input0    : [[1, 2], [1, 2]], [[1, 2], [1, 2]]
Sample Output0   : [[3, 6], [3, 6]]

Sample Input1    : [[1, 1], [1, 1]], [[1, 2, 1], [1, 2, 1]]
Sample Output1   : [2, 4, 2], [2, 4, 2]

Sample Input2    : [[1, 1], [1, 1]], [[1, 2], [1, 2], [1, 2]]
Sample Output2   : Cannot multiply the matrices. Incorrect dimensions.

Solution Key

def format_matrix(matrix):
    return "\n".join((("{:<5}"*len(row)).format(*row))for row in matrix)

def matrixmulti(X, Y):
    result = [[0 for col in range(len(Y[0]))] for row in range(len(X))]

    if  len(X[0]) != len(Y):
        print ("Cannot multiply the matrices. Incorrect dimensions.")
        return

    for i in range(len(X)):
        for j in range(len(Y[0])):
            for k in range(len(Y)):
                result[i][j] += X[i][k] * Y[k][j]

    print(format_matrix(result))
    return result

CloudCoder Exercise

http://j.mp/matrixMultiplyCC

Pre-Lab Questions

1. How to initialize a matrix (5 by 5) so that all its entries are equal to the number 10? What is the one line code for this?

2. Write a program to test whether the given matrix is a square matrix or not.

3. Write a program to test whether the given two matrices (say a and b), the matrix product operation a * b is possible or not.

Post-lab Questions

Bonus 1

1. Fix the failing test case in the following cyberdojo session - http://j.mp/randomMatrixCD

2. Use the functions to write a randomize_matrix function to generate a square matrix of size 5

3. Is the matrix creation the most efficient? Are you able to create a size of 22000 by 22000 before CyberDojo times out?

Bonus 2

Consider a two-dimensional matrix containing integer entries in which all rows and all columns are sorted in ascending order. For example:

 1 12 43 87
 9 25 47 88
17 38 48 92
45 49 74 95

Your task is to write a program that takes a matrix as describe above, and a target integer, and determines if the target integer is present in the matrix.

Related Material

CD Link

http://10.100.8.8/kata/edit/3A77017D5C?avatar=dolphin (Poongothai) http://cyberdojo1.kgfsl.com/kata/edit/F52E98217E?avatar=raccoon (Ashok)

Transpose a matrix

• CloudCoder Problem: http://j.mp/stransposeCC and http://j.mp/transposeCC

• The video key for it (using visualizer) - http://j.mp/transposeVideoKey