LeetCode in Kotlin

2047. Number of Valid Words in a Sentence

Easy

A sentence consists of lowercase letters ('a' to 'z'), digits ('0' to '9'), hyphens ('-'), punctuation marks ('!', '.', and ','), and spaces (' ') only. Each sentence can be broken down into one or more tokens separated by one or more spaces ' '.

A token is a valid word if all three of the following are true:

• It only contains lowercase letters, hyphens, and/or punctuation (no digits).
• There is at most one hyphen '-'. If present, it must be surrounded by lowercase characters ("a-b" is valid, but "-ab" and "ab-" are not valid).
• There is at most one punctuation mark. If present, it must be at the end of the token ("ab,", "cd!", and "." are valid, but "a!b" and "c.," are not valid).

Examples of valid words include "a-b.", "afad", "ba-c", "a!", and "!".

Given a string sentence, return the number of valid words in sentence.

Example 1:

Input: sentence = “cat and dog”

Output: 3

Explanation: The valid words in the sentence are “cat”, “and”, and “dog”.

Example 2:

Input: sentence = “!this 1-s b8d!”

Output: 0

Explanation: There are no valid words in the sentence.

“!this” is invalid because it starts with a punctuation mark.

“1-s” and “b8d” are invalid because they contain digits.

Example 3:

Input: sentence = “alice and bob are playing stone-game10”

Output: 5

Explanation: The valid words in the sentence are “alice”, “and”, “bob”, “are”, and “playing”. “stone-game10” is invalid because it contains digits.

Constraints:

• 1 <= sentence.length <= 1000
• sentence only contains lowercase English letters, digits, ' ', '-', '!', '.', and ','.
• There will be at least 1 token.

Solution

class Solution {
    fun countValidWords(sentence: String): Int {
        val tokens = sentence.split("\\s+".toRegex()).dropLastWhile { it.isEmpty() }.toTypedArray()
        var count = 0
        for (token in tokens) {
            var hyphenCount = 0
            var punctuationMarkCount = 0
            var valid = true
            if (token.isEmpty() || token == "") {
                continue
            }
            for (i in 0 until token.length) {
                if (token[i] == '-') {
                    hyphenCount++
                    if (hyphenCount > 1 || i == 0 || i == token.length - 1 ||
                        !Character.isAlphabetic(token[i - 1].code) ||
                        !Character.isAlphabetic(token[i + 1].code)
                    ) {
                        valid = false
                        break
                    }
                } else if (token[i] == '!' || token[i] == '.' || token[i] == ',') {
                    punctuationMarkCount++
                    if (punctuationMarkCount > 1 || i != token.length - 1) {
                        valid = false
                        break
                    }
                } else if (Character.isDigit(token[i])) {
                    valid = false
                    break
                }
            }
            if (valid) {
                count++
            }
        }
        return count
    }
}

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