290-Word-Pattern.md

290. Word Pattern

2017-03-13

Given a pattern and a string str, find if str 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 str.

Examples:

1. pattern = "abba", str = "dog cat cat dog" should return true.
2. pattern = "abba", str = "dog cat cat fish" should return false.
3. pattern = "aaaa", str = "dog cat cat dog" should return false.
4. pattern = "abba", str = "dog dog dog dog" should return false.

Notes: You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

Solution

class Solution {
    func wordPattern(_ pattern: String, _ str: String) -> Bool {
        let array = str.components(separatedBy: " ")
        guard pattern.characters.count == array.count else { return false }
        var dict = [String: String]()
        for (i, char) in pattern.characters.enumerated() {
            let word = array[i]
            let c = char.description
            if let test = dict[c] {
                guard test == word else { return false }
            } else  {
                if dict.values.contains(word) {
                    return false
                } else {
                    dict[c] = word
                }
            }
        }
        return true

    }
}