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Report Spam Message

Difficulty: Medium

Problem Description

You are given an array of strings message and an array of strings bannedWords. An array of words is considered spam if there are at least two words in it that exactly match any word in bannedWords. Return true if the array message is spam, and false otherwise.

Key Insights

  • A spam message contains at least two words that are found in the list of banned words.
  • We can efficiently check for the presence of banned words using a set data structure.
  • Counts of matched banned words can be tracked to determine if the spam condition is met.

Space and Time Complexity

Time Complexity: O(m + b), where m is the length of the message array and b is the length of the bannedWords array, due to the need to iterate through both arrays.

Space Complexity: O(b), for storing the banned words in a set.

Solution

To solve the problem, we can use the following approach:

  1. Convert the bannedWords array into a set for O(1) average time complexity on lookups.
  2. Initialize a counter to keep track of how many banned words are found in the message.
  3. Loop through each word in the message and check if it exists in the banned words set.
  4. Increment the counter for each match found.
  5. If the counter reaches 2, return true as the message is considered spam.
  6. If the loop completes and the counter is less than 2, return false.

Code Solutions

def is_spam_message(message, bannedWords):
    banned_set = set(bannedWords)  # Convert bannedWords to a set for fast lookup
    count = 0  # Initialize counter for banned words found
    
    for word in message:  # Iterate through each word in the message
        if word in banned_set:  # Check if the word is in the banned set
            count += 1  # Increment count on match
            if count >= 2:  # If count reaches 2, return True
                return True
                
    return False  # If we finish the loop without finding 2 matches, return False
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