JavaScriptWordPattern.md

JavaScript Word Pattern

Challenge

Given a pattern and a string s, find if s follows the same pattern.

Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in s.

1^st Example

Input: pattern = 'abba', s = 'dog cat cat dog'
Output: true

2^nd Example

Input: pattern = 'abba', s = 'dog cat cat fish'
Output: false

3^rd Example

Input: pattern = 'aaaa', s = 'dog cat cat dog'
Output: false

Constraints

• 1 <= pattern.length <= 300
• 1 <= s.length <= 3000
• pattern contains only lower-case English letters.
• s contains only lowercase English letters and spaces ' '.
• s does not contain any leading or trailing spaces.
• All the words in s are separated by a single space.

Solution

const wordPattern = (pattern, s) => {
    const arr = s.split(' '),
          map = {};

    if (arr.length !== pattern.length || new Set([...pattern]).size !== new Set(arr).size) {
        return false;
    }

    for (let i = 0; i < pattern.length; i++) {
        if (!map[pattern[i]]) {
            map[pattern[i]] = arr[i];
        } else if (map[pattern[i]] !== arr[i]) {
            return false;
        }
    }

    return true;
};

Explanation

I've built a function called wordPattern that takes two parameters: pattern and s (string). Its purpose is to check if the pattern matches the string by mapping each character in the pattern to a word in the string.

Inside the function, the string s is split into an array of words using the split() method and stored in the variable arr. An empty object called map is also created.

The function then checks if the length of the arr array is not equal to the length of the pattern or if the number of unique characters in the pattern is not equal to the number of unique words in arr. If either of these conditions is true, the function immediately returns false.

Next, a for loop is used to iterate through each character in the pattern. Inside the loop, it checks if the current character is already a key in the map object. If it is not, the character is added as a key in the map object, and the corresponding word in arr is added as the value.

If the current character is already a key in the map object, it checks if the value of the key matches the corresponding word in arr. If the values do not match, the function immediately returns false.

If the for loop completes without returning false, it means that the pattern matches the string, and the function returns true.

In summary, the wordPattern function checks if a given pattern matches a given string by mapping each character in the pattern to a word in the string. It returns true if the mapping is successful, and false otherwise.

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