290.word-pattern.java

/*
 * @lc app=leetcode id=290 lang=java
 *
 * [290] Word Pattern
 *
 * https://leetcode.com/problems/word-pattern/description/
 *
 * algorithms
 * Easy (35.41%)
 * Total Accepted:    165.3K
 * Total Submissions: 458.9K
 * Testcase Example:  '"abba"\n"dog cat cat dog"'
 *
 * 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.
 *
 * Example 1:
 *
 *
 * Input: pattern = "abba", str = "dog cat cat dog"
 * Output: true
 *
 * Example 2:
 *
 *
 * Input:pattern = "abba", str = "dog cat cat fish"
 * Output: false
 *
 * Example 3:
 *
 *
 * Input: pattern = "aaaa", str = "dog cat cat dog"
 * Output: false
 *
 * Example 4:
 *
 *
 * Input: pattern = "abba", str = "dog dog dog dog"
 * Output: false
 *
 * Notes:
 * You may assume pattern contains only lowercase letters, and str contains
 * lowercase letters that may be separated by a single space.
 *
 */
 class Solution {

    /**
    public boolean wordPattern(String pattern, String str) {
        String[] subStr = str.split(" ");

        if (pattern.length() != subStr.length) {
            return false;
        }

        Map<Character, String> mapping = new HashMap<>();
        Map<String, Character> reverseMapping = new HashMap<>();

        for (int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);
            String s = subStr[i];

            if (mapping.containsKey(c) && !mapping.get(c).equals(s)) {
                return false;
            }

            if (reverseMapping.containsKey(s) && reverseMapping.get(s) != c) {
                return false;
            }

            mapping.put(c, s);
            reverseMapping.put(s, c);
        }

        return true;
    }
    */

    public boolean wordPattern(String pattern, String str) {
        String[] subStr = str.split(" ");

        if (pattern.length() != subStr.length) {
            return false;
        }

        Map<Character, String> mapping = new HashMap<>();

        for (int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);
            String s = subStr[i];

            if (mapping.containsKey(c) && !mapping.get(c).equals(s)) {
                return false;
            }

            if (!mapping.containsKey(c) && mapping.containsValue(s)) {
                return false;
            }

            mapping.put(c, s);
        }

        return true;
    }
}