A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 x 99. Let's try to find the largest palindrome made from the product of two 3-digit numbers.
We will create an array to hold 3-digit numbers from 100 to 999 using our favorite NumPy function arange.
Create a 3-digit numbers array.
Check the first and last element of the array with the
assert_equalfunction from thenumpy.testingpackage:a = numpy.arange(100, 1000) numpy.testing.assert_equal(100, a[0]) numpy.testing.assert_equal(999, a[-1])
Create the products array
Now, we will create an array to hold all the possible products of the elements of the 3-digits array with itself. We can accomplish this with the
outerfunction. The resulting array needs to be flattened withravel, to be able to easily iterate over it. Call thesortmethod on the array to make sure the array is properly sorted. After that, we can do some sanity checks...