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How to Solve Number of Valid Words in a Sentence Problem
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Start Free for WindowsEasy#2047
LeetCode ProblemNumber of Valid Words in a Sentence
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: Examples of valid words include "a-b.", "afad", "ba-c", "a!", and "!". Given a string sentence, return the number of valid words in sentence.
String
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Problem Breakdown
Understanding the Number of Valid Words in a Sentence Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
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: Examples of valid words include "a-b.", "afad", "ba-c", "a!", and "!". Given a string sentence, return the number of valid words in sentence.
EasyProblem #2047
LeetCodeNumber of Valid Words in a Sentence
Related Topics
String
How Phantom Code Helps
Get real-time assistance for Number of Valid Words in a Sentence problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
sentence = "cat and dog"
Output
3
# Example 2
Input
sentence = "!this 1-s b8d!"
Output
0
# Example 3
Input
sentence = "alice and bob are playing stone-game10"
Output
5
Constraints
1 <= sentence.length <= 1000
sentence only contains lowercase English letters, digits, ' ', '-', '!', '.', and ','.
There will be at least 1 token.
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Solve Number of Valid Words in a Sentence — A sentence consists of lowercase letters ('a' to 'z'), digits ('0' to '9'), hyph...
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def solve(input):
# Optimal O(n) solution
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Phantom Code catches common mistakes like off-by-one errors, missing edge cases, incorrect base conditions, and suboptimal approaches. It provides clean, well-structured code that handles all edge cases.
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The AI provides structured guidance: first the approach (what algorithm/data structure to use and why), then the implementation with clean code, and finally complexity analysis. This helps you think clearly even under pressure.
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