Word Pattern

Description

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.

 

Example 1:

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

Example 2:

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

Example 3:

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

Example 4:

Input: pattern = "abba", s = "dog dog dog dog"
Output: false

 

Constraints:

• 1 <= pattern.length <= 300
• pattern contains only lower-case English letters.
• 1 <= s.length <= 3000
• s contains only lower-case 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(javascript)

const wordPattern = (pattern, str) => {
  const patternMap = Array.prototype.reduce.call(pattern, (map, c, index) => {
    if (map[c]) {
      map[c]++
    } else {
      map[c] = 1
    }
    return map
  }, {})
  const wordArr = str.split(' ')
  if (wordArr.length !== pattern.length) {
    return false
  }
  const wordMap = wordArr.reduce((map, word) => {
    if (map[word]) {
      map[word]++
    } else {
      map[word] = 1
    }
    return map
  }, {})
  for (let i = 0; i < pattern.length; i++) {
    if (patternMap[pattern[i]] !== wordMap[wordArr[i]]) {
      return false
    }
  }
  return true
}