WordPattern.java

import java.rmi.MarshalledObject;
import java.util.HashMap;
import java.util.Map;

/**
 * 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:
 * pattern = "abba", str = "dog cat cat dog" should return true.
 * pattern = "abba", str = "dog cat cat fish" should return false.
 * pattern = "aaaa", str = "dog cat cat dog" should return false.
 * 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.
 * 
 * Tags: Hash Table
 * Similar Problems: (E) Isomorphic Strings (H) Word Pattern II
 */
class WordPattern {
    public boolean wordPattern(String pattern, String str) {
        if (pattern == null || str == null) return false;
        String[] words = str.split(" ");
        if (words.length != pattern.length()) return false;

        Map<Object, Integer> map = new HashMap<>(pattern.length());

        for (Integer i = 0; i < words.length; i++) { // use Integer to avoid autoboxing-same-value-to-different-objects-problem
            if (map.put(pattern.charAt(i), i) != map.put(words[i], i)) // check previous put value
                return false;
        }

        return true;
    }

    public static void main(String[] args) {
        WordPattern w = new WordPattern();
        String[] patterns = new String[]{"abba", "abba", "aaaa", "abba", "itwasthebestoftimesitwastheworstoftimesitwastheageofwisdomitwastheageoffoolishnessitwastheepochofbeliefitwastheepochofincredulityitwastheseasonoflightitwastheseasonofdarknessitwasthespringofhopeitwasthewinterofdespair"};
        String[] strings = new String[]{"dog cat cat dog", "dog cat cat fish", "dog cat cat dog", "dog dog dog dog", "i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee bbbbbbbbbbbbbbbbbb eeeeeeeeeee sssss tttttttttttttttt oo fffffffff tttttttttttttttt i mmm eeeeeeeeeee sssss i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee wwww oo rrrrrrrrrrrrrr sssss tttttttttttttttt oo fffffffff tttttttttttttttt i mmm eeeeeeeeeee sssss i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee aa gggggggggggggg eeeeeeeeeee oo fffffffff wwww i sssss ddddddddddd oo mmm i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee aa gggggggggggggg eeeeeeeeeee oo fffffffff fffffffff oo oo llllllll i sssss hhhhhhhhhhhhhhhhhhhhhhh nnnnnn eeeeeeeeeee sssss sssss i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee eeeeeeeeeee pppp oo cccccccccccc hhhhhhhhhhhhhhhhhhhhhhh oo fffffffff bbbbbbbbbbbbbbbbbb eeeeeeeeeee llllllll i eeeeeeeeeee fffffffff i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee eeeeeeeeeee pppp oo cccccccccccc hhhhhhhhhhhhhhhhhhhhhhh oo fffffffff i nnnnnn cccccccccccc rrrrrrrrrrrrrr eeeeeeeeeee ddddddddddd uuuuuuuuuu llllllll i tttttttttttttttt yyyyyyyyyyy i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee sssss eeeeeeeeeee aa sssss oo nnnnnn oo fffffffff llllllll i gggggggggggggg hhhhhhhhhhhhhhhhhhhhhhh tttttttttttttttt i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee sssss eeeeeeeeeee aa sssss oo nnnnnn oo fffffffff ddddddddddd aa rrrrrrrrrrrrrr kkkkkkkkk nnnnnn eeeeeeeeeee sssss sssss i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee sssss pppp rrrrrrrrrrrrrr i nnnnnn gggggggggggggg oo fffffffff hhhhhhhhhhhhhhhhhhhhhhh oo pppp eeeeeeeeeee i tttttttttttttttt wwww aa sssss tttttttttttttttt hhhhhhhhhhhhhhhhhhhhhhh eeeeeeeeeee wwww i nnnnnn tttttttttttttttt eeeeeeeeeee rrrrrrrrrrrrrr oo fffffffff ddddddddddd eeeeeeeeeee sssss pppp aa i rrrrrrrrrrrrrr"};
        for (int i = 0; i < patterns.length; i++) {
            System.out.println(w.wordPattern(patterns[i], strings[i]));
        }
    }
}