LeetCode 819: Most Common Word Solution

Master LeetCode problem 819 (Most Common Word), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

819. Most Common Word

Easy

Array Hash Table String Counting

Problem Explanation

Explanation

To solve this problem, we can follow these steps:

Preprocess the paragraph to extract words and convert them to lowercase.
Create a set of banned words for efficient lookup.
Count the frequency of each non-banned word using a hashmap.
Find the word with the highest frequency that is not banned.

Time complexity: O(n) where n is the length of the paragraph Space complexity: O(n) for storing the word frequencies

Solution Code

import java.util.*;

class Solution {
    public String mostCommonWord(String paragraph, String[] banned) {
        Set<String> bannedSet = new HashSet<>(Arrays.asList(banned));
        Map<String, Integer> wordCount = new HashMap<>();
        
        String[] words = paragraph.toLowerCase().split("[^a-zA-Z]+");
        
        for (String word : words) {
            if (!bannedSet.contains(word)) {
                wordCount.put(word, wordCount.getOrDefault(word, 0) + 1);
            }
        }
        
        int maxCount = 0;
        String mostCommonWord = "";
        
        for (String word : wordCount.keySet()) {
            if (wordCount.get(word) > maxCount) {
                maxCount = wordCount.get(word);
                mostCommonWord = word;
            }
        }
        
        return mostCommonWord;
    }
}

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