290.Word Pattern

package Leetcode.HashTable;

import java.util.HashMap;
import java.util.Map;

/**
 * @author zhengxingxing
 * @date 2024/11/09
 */
public class WordPattern {
    public static boolean wordPattern(String pattern, String s) {
        // Split the input string into an array of words
        String[] words = s.split(" ");

        // Check if the length of pattern matches the number of words
        // If not, they can't possibly follow the same pattern
        if(pattern.length() != words.length){
            return false;
        }

        // Create two HashMaps for bidirectional mapping
        // charToWord: maps each character in pattern to its corresponding word
        Map<Character, String> charToWord = new HashMap<>();
        // wordToChar: maps each word to its corresponding character in pattern
        Map<String, Character> wordToChar = new HashMap<>();

        // Iterate through each character in pattern and its corresponding word
        for (int i = 0; i < pattern.length(); i++) {
            char c = pattern.charAt(i);
            String word = words[i];

            // Check character to word mapping
            if(charToWord.containsKey(c)){
                // If this character has been mapped before,
                // verify it maps to the same word
                if(!charToWord.get(c).equals(word)){
                    return false;  // Violation: same char maps to different words
                }
            }else{
                // If this is a new character, add the mapping
                charToWord.put(c, word);
            }

            // Check word to character mapping
            if(wordToChar.containsKey(word)){
                // If this word has been mapped before,
                // verify it maps to the same character
                if(wordToChar.get(word) != c){
                    return false;  // Violation: same word maps to different chars
                }
            }else{
                // If this is a new word, add the mapping
                wordToChar.put(word, c);
            }
        }
        // If we reach here, all mappings are valid
        return true;
    }

    public static void main(String[] args) {
        // Test Case 1: Should return true
        // Pattern "abba" matches with "dog cat cat dog"
        String pattern1 = "abba";
        String s1 = "dog cat cat dog";
        System.out.println("Test Case 1:");
        System.out.println("pattern = " + pattern1);
        System.out.println("s = " + s1);
        System.out.println("Result: " + wordPattern(pattern1, s1));
        System.out.println();

        // Test Case 2: Should return false
        // Pattern "abba" doesn't match with "dog cat cat fish"
        String pattern2 = "abba";
        String s2 = "dog cat cat fish";
        System.out.println("Test Case 2:");
        System.out.println("pattern = " + pattern2);
        System.out.println("s = " + s2);
        System.out.println("Result: " + wordPattern(pattern2, s2));
        System.out.println();

        // Test Case 3: Should return false
        // Pattern "aaaa" doesn't match with "dog cat cat dog"
        String pattern3 = "aaaa";
        String s3 = "dog cat cat dog";
        System.out.println("Test Case 3:");
        System.out.println("pattern = " + pattern3);
        System.out.println("s = " + s3);
        System.out.println("Result: " + wordPattern(pattern3, s3));
    }
}