884. Uncommon Words from Two Sentences

[mah-shamim]

Topics: Hash Table, String, Counting

A sentence is a string of single-space separated words where each word consists only of lowercase letters.

A word is uncommon if it appears exactly once in one of the sentences, and does not appear in the other sentence.

Given two sentences s1 and s2, return a list of all the uncommon words. You may return the answer in any order.

Example 1:

• Input: s1 = "this apple is sweet", s2 = "this apple is sour"
• Output: ["sweet","sour"]
• Explanation: The word "sweet" appears only in s1, while the word "sour" appears only in s2.

Example 2:

• Input: s1 = "apple apple", s2 = "banana"
• Output: ["banana"]

Constraints:

• 1 <= s1.length, s2.length <= 200
• s1 and s2 consist of lowercase English letters and spaces.
• s1 and s2 do not have leading or trailing spaces.
• All the words in s1 and s2 are separated by a single space.

[basharul-siddike]

We can follow these steps:

1. Break the sentences into words: Split both s1 and s2 into individual words.
2. Count the occurrences of each word: Use an associative array (hash table) to count how many times each word appears across both sentences.
3. Filter uncommon words: Find words that appear exactly once in the combined set of words from both sentences and do not appear in both sentences.

Approach:

• Use the explode function to split the sentences into arrays of words.
• Use an associative array to count the frequency of each word.
• Return the words that have a count of 1.

Let's implement this solution in PHP: 884. Uncommon Words from Two Sentences

<?php
/**
 * @param String $s1
 * @param String $s2
 * @return String[]
 */
function uncommonFromSentences($s1, $s2) {
    // Split the sentences into words
    $words1 = explode(' ', $s1);
    $words2 = explode(' ', $s2);

    // Initialize an array to hold the frequency of each word
    $wordCount = array();

    // Count the occurrences of each word from both sentences
    foreach ($words1 as $word) {
        if (isset($wordCount[$word])) {
            $wordCount[$word]++;
        } else {
            $wordCount[$word] = 1;
        }
    }
    
    foreach ($words2 as $word) {
        if (isset($wordCount[$word])) {
            $wordCount[$word]++;
        } else {
            $wordCount[$word] = 1;
        }
    }

    // Collect the uncommon words (words that appear only once)
    $result = array();
    foreach ($wordCount as $word => $count) {
        if ($count == 1) {
            $result[] = $word;
        }
    }

    return $result;
}

// Test cases
$s1 = "this apple is sweet";
$s2 = "this apple is sour";
print_r(uncommonFromSentences($s1, $s2)); // Output: ["sweet", "sour"]

$s1 = "apple apple";
$s2 = "banana";
print_r(uncommonFromSentences($s1, $s2)); // Output: ["banana"]
?>

Explanation:

1. Splitting the sentences: We use explode(' ', $s1) and explode(' ', $s2) to split the sentences into arrays of words.
2. Counting occurrences: We loop through both arrays of words, incrementing the count of each word in the associative array $wordCount.
3. Filtering uncommon words: We then check for words that have a count of exactly 1 in the $wordCount array and add them to the result array.

Example Walkthrough:

• For s1 = "this apple is sweet" and s2 = "this apple is sour", after counting, the associative array $wordCount will look like:

  Array (
    [this] => 2
    [apple] => 2
    [is] => 2
    [sweet] => 1
    [sour] => 1
  )
  

  The words with a count of 1 are sweet and sour, so the result is ["sweet", "sour"].

Time Complexity:

• O(n + m), where n is the number of words in s1 and m is the number of words in s2. This is because we iterate through all the words in both sentences once to count the occurrences.

Space Complexity:

• O(n + m), where n and m are the number of words in s1 and s2. We store all the words in an associative array to track their counts.

[mah-shamim]

We can follow these steps:

1. **Break the sentences into words**: Split both `s1` and `s2` into individual words.

2. **Count the occurrences of each word**: Use an associative array (hash table) to count how many times each word appears across both sentences.

3. **Filter uncommon words**: Find words that appear exactly once in the combined set of words from both sentences and do not appear in both sentences.

Approach:

* Use the `explode` function to split the sentences into arrays of words.

* Use an associative array to count the frequency of each word.

* Return the words that have a count of 1.

Let's implement this solution in PHP: 884. Uncommon Words from Two Sentences

<?php
/**
 * @param String $s1
 * @param String $s2
 * @return String[]
 */
function uncommonFromSentences($s1, $s2) {
    // Split the sentences into words
    $words1 = explode(' ', $s1);
    $words2 = explode(' ', $s2);

    // Initialize an array to hold the frequency of each word
    $wordCount = array();

    // Count the occurrences of each word from both sentences
    foreach ($words1 as $word) {
        if (isset($wordCount[$word])) {
            $wordCount[$word]++;
        } else {
            $wordCount[$word] = 1;
        }
    }
    
    foreach ($words2 as $word) {
        if (isset($wordCount[$word])) {
            $wordCount[$word]++;
        } else {
            $wordCount[$word] = 1;
        }
    }

    // Collect the uncommon words (words that appear only once)
    $result = array();
    foreach ($wordCount as $word => $count) {
        if ($count == 1) {
            $result[] = $word;
        }
    }

    return $result;
}

// Test cases
$s1 = "this apple is sweet";
$s2 = "this apple is sour";
print_r(uncommonFromSentences($s1, $s2)); // Output: ["sweet", "sour"]

$s1 = "apple apple";
$s2 = "banana";
print_r(uncommonFromSentences($s1, $s2)); // Output: ["banana"]
?>

Explanation:

1. **Splitting the sentences**: We use `explode(' ', $s1)` and `explode(' ', $s2)` to split the sentences into arrays of words.

2. **Counting occurrences**: We loop through both arrays of words, incrementing the count of each word in the associative array `$wordCount`.

3. **Filtering uncommon words**: We then check for words that have a count of exactly 1 in the `$wordCount` array and add them to the result array.

Example Walkthrough:

* For `s1 = "this apple is sweet"` and `s2 = "this apple is sour"`, after counting, the associative array `$wordCount` will look like:
  ```
  Array (
    [this] => 2
    [apple] => 2
    [is] => 2
    [sweet] => 1
    [sour] => 1
  )
  ```
  
  
      
        
      
  
        
      
  
      
    
  The words with a count of 1 are `sweet` and `sour`, so the result is `["sweet", "sour"]`.

Time Complexity:

* **O(n + m)**, where `n` is the number of words in `s1` and `m` is the number of words in `s2`. This is because we iterate through all the words in both sentences once to count the occurrences.

Space Complexity:

* **O(n + m)**, where `n` and `m` are the number of words in `s1` and `s2`. We store all the words in an associative array to track their counts.

Thanks to solve the problem of finding uncommon words from two sentences

[basharul-siddike]

We can follow these steps:

1. **Break the sentences into words**: Split both `s1` and `s2` into individual words.

2. **Count the occurrences of each word**: Use an associative array (hash table) to count how many times each word appears across both sentences.

3. **Filter uncommon words**: Find words that appear exactly once in the combined set of words from both sentences and do not appear in both sentences.

Approach:

* Use the `explode` function to split the sentences into arrays of words.

* Use an associative array to count the frequency of each word.

* Return the words that have a count of 1.

Let's implement this solution in PHP: 884. Uncommon Words from Two Sentences

<?php
/**
 * @param String $s1
 * @param String $s2
 * @return String[]
 */
function uncommonFromSentences($s1, $s2) {
    // Split the sentences into words
    $words1 = explode(' ', $s1);
    $words2 = explode(' ', $s2);

    // Initialize an array to hold the frequency of each word
    $wordCount = array();

    // Count the occurrences of each word from both sentences
    foreach ($words1 as $word) {
        if (isset($wordCount[$word])) {
            $wordCount[$word]++;
        } else {
            $wordCount[$word] = 1;
        }
    }
    
    foreach ($words2 as $word) {
        if (isset($wordCount[$word])) {
            $wordCount[$word]++;
        } else {
            $wordCount[$word] = 1;
        }
    }

    // Collect the uncommon words (words that appear only once)
    $result = array();
    foreach ($wordCount as $word => $count) {
        if ($count == 1) {
            $result[] = $word;
        }
    }

    return $result;
}

// Test cases
$s1 = "this apple is sweet";
$s2 = "this apple is sour";
print_r(uncommonFromSentences($s1, $s2)); // Output: ["sweet", "sour"]

$s1 = "apple apple";
$s2 = "banana";
print_r(uncommonFromSentences($s1, $s2)); // Output: ["banana"]
?>

Explanation:

1. **Splitting the sentences**: We use `explode(' ', $s1)` and `explode(' ', $s2)` to split the sentences into arrays of words.

2. **Counting occurrences**: We loop through both arrays of words, incrementing the count of each word in the associative array `$wordCount`.

3. **Filtering uncommon words**: We then check for words that have a count of exactly 1 in the `$wordCount` array and add them to the result array.

Example Walkthrough:

* For `s1 = "this apple is sweet"` and `s2 = "this apple is sour"`, after counting, the associative array `$wordCount` will look like:

Array (
[this] => 2
[apple] => 2
[is] => 2
[sweet] => 1
[sour] => 1
)

    
      
    

      
    

    
  
The words with a count of 1 are `sweet` and `sour`, so the result is `["sweet", "sour"]`.

Time Complexity:

* **O(n + m)**, where `n` is the number of words in `s1` and `m` is the number of words in `s2`. This is because we iterate through all the words in both sentences once to count the occurrences.

Space Complexity:

* **O(n + m)**, where `n` and `m` are the number of words in `s1` and `s2`. We store all the words in an associative array to track their counts.

Thanks to solve the problem of finding uncommon words from two sentences

Thanks