Good keys

Weekly Challenge 282

Each week Mohammad S. Anwar sends out The Weekly Challenge, a chance for all of us to come up with solutions to two weekly tasks. My solutions are written in Python first, and then converted to Perl. It's a great way for us all to practice some coding.

Challenge, My solutions

Task 1: Good Integer

Task

You are given a positive integer, $int, having 3 or more digits.

Write a script to return the Good Integer in the given integer or -1 if none found. A good integer is exactly three consecutive matching digits.

My solution

I original thought this task could be done with a regular expression pattern, but it seems I was wrong. I'll be looking at other TPW members to see if they can do it that way.

For this task I have a variable pos that iterates from 0 to three less than the length of the string. I then check four things:

1. The digit at the current position is the same as the one in the next position.
2. The digit at the current position is the same as the one in the second next position.
3. The position is 0 (meaning there are no digits before the current one) or the previous digit is not the same as the current digit.
4. The position is 3 less than the length (meaning there is no digit after the current three digits) or the third next digit is not the same as the current digit.

If these are all true, I return those three digits. This is done as a string in Python, because '000' is not a real integer. If the iterator is exhausted, I return -1.

def good_integer(n: int) -> str:
    value = str(n)
    length = len(value)

    for pos in range(length-2):
        if (
            value[pos] == value[pos+1]
            and value[pos] == value[pos+2]
            and (pos == 0 or value[pos] != value[pos-1])
            and (pos + 3 == length or value[pos] != value[pos+3])
        ):
            return value[pos:pos+3]

    return '-1'

Examples

$ ./ch-1.py 12344456
444

$ ./ch-1.py 1233334
-1

$ ./ch-1.py 10020003
000

Task 2: Changing Keys

Task

You are given an alphabetic string, $str, as typed by user.

Write a script to find the number of times user had to change the key to type the given string. Changing key is defined as using a key different from the last used key. The "shift" and "caps lock" keys won’t be counted.

My solution

Fun fact. When I get a new keyboard (every few years), I see how long it takes before I rip the caps lock key out. Most keyboards don't last a day!

For this task, I convert the string to lower case and start with two variables. The current_key value is the current key pressed, and is initialized with the first letter from our input. The changes variable is the number of key changes I make, and starts with 0.

I then loop through each letter in the input string. If that letter is different from current_key, I update it with the new letter, and increment changes by 1.

def key_changes(s: str) -> int:
    s = s.lower()
    current_key = s[0]
    changes = 0

    for letter in s:
        if letter != current_key:
            current_key = letter
            changes += 1

    return changes

Examples

$ ./ch-2.py pPeERrLl
3

$ ./ch-2.py rRr
0

$ ./ch-2.py GoO
1