The solution to Challenge #4 of AdventJS 2023
The solution to the previous challenge
The solution to the next challenge
Challenge Description
In 🎅 Santa's workshop, some Christmas messages have been written peculiarly: the words within the brackets must be read backward.
Santa needs these messages to be correctly formatted. Your task is to write a function that takes a string and reverses the characters within each pair of parentheses, removing the parentheses as well.
However, bear in mind that there may be nested parentheses, so you should reverse the characters in the correct order.
const a = decode('hola (odnum)')
console.log(a)
const b = decode('(olleh) (dlrow)!')
console.log(b)
const c = decode('sa(u(cla)atn)s')
console.log(c)
Notes:
The input strings will always be well-formed with parentheses that match correctly, you do not need to validate them.
There should not be any parentheses left in the final message.
The maximum nesting level is 2.
Analysis
In this exercise, the goal is to reverse the letters that are within parentheses. If there are nested parentheses, you'll need to reorder multiple times, depending on the number of nested levels.
- Message (
message): A string with the message in which we must search and reorder the letters that are inside parentheses.
Output
- The correctly ordered string
Considerations
Solution
To cover all cases and considerations, you should start by looking for the last opening parenthesis ( and then match it with the first closing parenthesis ) after the opening one. Extract the letters that are inside and reorder them in reverse.
Then repeat the process with the resulting string, so a while loop can be used to achieve this.
Code
function decode(message) {
let init, end;
while (init !== -1 || end !== -1) {
init = message.lastIndexOf("(");
end = message.indexOf(")", init);
const encoded = message.substring(init, end + 1);
const decoded = encoded.split("").slice(1, -1).reverse().join("");
message = message.replace(encoded, decoded);
}
return message;
}
Solution by cristianstu:
function decode(message) {
const msg = message.replace(/\(([^()]*)\)/g, (_, match) =>
match.split('').reverse().join('')
);
return msg.includes('(') ? decode(msg) : msg;
}
Solution by TimmyElTaco:
function decode(message) {
let matches = [];
while (matches = message.match(/\(([^()]*)\)/)) {
matches = matches.map((word) => {
return word.split('').reverse().join('')
})
let string = matches[0].replace(/[()]/g, '');
message = message.replace(/\(([^()]*)\)/, string);
}
return message;
}
And that was the challenge for December 4th and its solutions. Do you have another alternative solution? Leave it in the comments!
