Question

Goal: Learn to write while loops.

Assignment: Assume a string is assigned to passphrase. Unfortunately, whoever wrote it did not read the

requirements correctly because they used special characters, which is not allowed. Passphrases need to be

alphanumeric only. Fortunately, they added most of these special characters to the end of the passphrase. Write

some code that assigns to passphrase the longest substring of the original passphrase that satisfies the

alphanumeric requirement. For example, if the original passphrase is abc$2\%$t$3$@$5,$ the new passphrase will be abc $2.$

You must use a while loop in this exercise.