Weekly Challenge: Reversing my broken keys

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Weekly Challenge 341

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: Broken Keyboard

Task

You are given a string containing English letters only and also you are given broken keys.

Write a script to return the total words in the given sentence can be typed completely.

My solution

On my keyboard, the only broken key is the Caps Lock key. It’s lasts a couple of hours before I dislike it and remove it 🙂

For this challenge, I convert all the input to lower case. I then set a variable called completed_words to 0. I loop through each word in the input_string variable. If it does not contain any of the letters in the broken_keys list (array in Perl), I increment the completed_words variable. 

def broken_keyboard(input_string: str, broken_keys: list[str]) -> int:
    input_string = input_string.lower()
    broken_keys = [key.lower() for key in broken_keys]

    completed_words = 0
    for word in input_string.split():
        if not any(char in broken_keys for char in word):
            completed_words += 1

    return completed_words

The Perl solution follows the same logic. 

sub main (@array) {
    my $input_string = lc shift @array;
    my @broken_keys = map { lc } @array;

    my $completed_words = 0;
    for my $word (split ' ', $input_string) {
        if (not grep { index($word, $_) != -1 } @broken_keys) {
            $completed_words++;
        }
    }

    say $completed_words;
}

Examples

$ ./ch-1.py 'Hello World' d
1

$ ./ch-1.py 'apple banana cherry' a e
0

$ ./ch-1.py 'Coding is fun'
3

$ ./ch-1.py 'The Weekly Challenge' a b
2

$ ./ch-1.py 'Perl and Python' p
1

Task 2: Reverse Prefix

Task

You are given a string, $str and a character in the given string, $char.

Write a script to reverse the prefix upto the first occurrence of the given $char in the given string $str and return the new string.

My solution

For this challenge, I start by finding the position of the first occurrence of the char character in the input_string variable, and store it in the pos variable. If it does not exist, I throw an error.

In Python, I can obtain the reverse of the string using -1 as the third parameter to the list comprehension value. 

def reverse_prefix(input_string: str, char: str) -> str:
    pos = input_string.find(char)

    if pos == -1:
        raise ValueError(f"Character '{char}' not found in input string.")

    return input_string[pos::-1] + input_string[pos+1:]

Perl provides the reverse function, which does what you would expect to. Along with substr function this can be used to reverse part of the string. 

sub main (@array) {
    my ( $input_string, $char ) = @array;

    my $pos = index( $input_string, $char );
    if ( $pos == -1 ) {
        die "Character '$char' not found in input string.n";
    }

    say reverse( substr( $input_string, 0, $pos + 1 ) )
      . substr( $input_string, $pos + 1 );
}

Examples

$ ./ch-2.py programming g
gorpramming

$ ./ch-2.py hello h
hello

$ ./ch-2.py abcdefghij h
hgfedcbaij

$ ./ch-2.py reverse s
srevere

$ ./ch-2.py perl r
repl

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