優達學城《計算機科學導論》 --判斷單位矩陣

# Given a list of lists representing a n * n matrix as input, 
# define a  procedure that returns True if the input is an identity matrix 
# and False otherwise.

# An IDENTITY matrix is a square matrix in which all the elements 
# on the principal/main diagonal are 1 and all the elements outside 
# the principal diagonal are 0. 
# (A square matrix is a matrix in which the number of rows 
# is equal to the number of columns)

def is_identity_matrix(matrix):
    if len(matrix)==len(matrix[0]):
        for i in range(len(matrix)):
            for j in range(len(matrix)):
                if i==j and matrix[i][j]!=1:
                    return 'FALSE'
                    break
                elif i!=j and matrix[i][j]!=0:
                    return 'FALSE'
                    break
                elif i==len(matrix)-1 and j==len(matrix)-1:
                    return 'TRUE'
    elif len(matrix)!=len(matrix[0]):
        return 'FALSE'
                
    #Write your code here

# Test Cases:

matrix1 = [[1,0,0,0],
           [0,1,0,0],
           [0,0,1,0],
           [0,0,0,1]]
print is_identity_matrix(matrix1)
#>>>True

matrix2 = [[1,0,0],
           [0,1,0],
           [0,0,0]]

print is_identity_matrix(matrix2)
#>>>False

matrix3 = [[2,0,0],
           [0,2,0],
           [0,0,2]]

print is_identity_matrix(matrix3)
#>>>False

matrix4 = [[1,0,0,0],
           [0,1,1,0],
           [0,0,0,1]]

print is_identity_matrix(matrix4)
#>>>False

matrix5 = [[1,0,0,0,0,0,0,0,0]]

print is_identity_matrix(matrix5)
#>>>False

matrix6 = [[1,0,0,0],  
           [0,1,0,1],  
           [0,0,1,0],  
           [0,0,0,1]]

print is_identity_matrix(matrix6)
#>>>False

matrix7 = [[1, -1, 1],
           [0, 1, 0],
           [0, 0, 1]]
print is_identity_matrix(matrix7)
#>>>False