diff --git a/src/main/java/com/thealgorithms/strings/WordLadder.java b/src/main/java/com/thealgorithms/strings/WordLadder.java index 707fdfc6..084a682b 100644 --- a/src/main/java/com/thealgorithms/strings/WordLadder.java +++ b/src/main/java/com/thealgorithms/strings/WordLadder.java @@ -4,58 +4,28 @@ import java.util.HashSet; import java.util.LinkedList; import java.util.List; import java.util.Queue; +import java.util.Set; -/* - **Problem Statement:** - A transformation sequence from word beginWord to word endWord using a dictionary wordList is a - sequence of words beginWord -> s1 -> s2 -> ... -> sk such that: - - Every adjacent pair of words differs by a single letter. - Every si for 1 <= i <= k is in wordList. Note that beginWord does not need to be in wordList. - sk == endWord - Given two words, beginWord and endWord, and a dictionary wordList, return the number of words in - the shortest transformation sequence from beginWord to endWord, or 0 if no such sequence exists. - - **Example 1:** - Input: beginWord = "hit", endWord = "cog", wordList = ["hot","dot","dog","lot","log","cog"] - Output: 5 - Explanation: One shortest transformation sequence is "hit" -> "hot" -> "dot" -> "dog" -> cog", - which is 5 words long. - - **Example 2:** - Input: beginWord = "hit", endWord = "cog", wordList = ["hot","dot","dog","lot","log"] - Output: 0 - Explanation: The endWord "cog" is not in wordList, therefore there is no valid transformation - sequence. - - **Constraints:** - 1 <= beginWord.length <= 10 - endWord.length == beginWord.length - 1 <= wordList.length <= 5000 - wordList[i].length == beginWord.length - beginWord, endWord, and wordList[i] consist of lowercase English letters. - beginWord != endWord - All the words in wordList are unique. +/** + * Class to find the shortest transformation sequence from a beginWord to an endWord using a dictionary of words. + * A transformation sequence is a sequence of words where each adjacent pair differs by exactly one letter. */ - -final class WordLadder { +public final class WordLadder { private WordLadder() { } /** - * This function finds the ladderLength + * Finds the shortest transformation sequence from beginWord to endWord. * - * @param beginWord: Starting word of the ladder - * @param endWord: Ending word of the ladder - * @param wordList: This list contains the words which needs to be included - * in ladder. - * @return ladderLength: This function will return the ladderLength(level) - * if the endword is there. Otherwise, will return the length as 0. + * @param beginWord the starting word of the transformation sequence + * @param endWord the target word of the transformation sequence + * @param wordList a list of words that can be used in the transformation sequence + * @return the number of words in the shortest transformation sequence, or 0 if no such sequence exists */ public static int ladderLength(String beginWord, String endWord, List wordList) { - HashSet set = new HashSet<>(wordList); + Set wordSet = new HashSet<>(wordList); - if (!set.contains(endWord)) { + if (!wordSet.contains(endWord)) { return 0; } @@ -66,25 +36,25 @@ final class WordLadder { while (!queue.isEmpty()) { int size = queue.size(); for (int i = 0; i < size; i++) { - String curr = queue.poll(); - char[] wordsChars = curr.toCharArray(); - for (int j = 0; j < wordsChars.length; j++) { - char originalChars = wordsChars[j]; + String currentWord = queue.poll(); + char[] currentWordChars = currentWord.toCharArray(); + for (int j = 0; j < currentWordChars.length; j++) { + char originalChar = currentWordChars[j]; for (char c = 'a'; c <= 'z'; c++) { - if (wordsChars[j] == c) { + if (currentWordChars[j] == c) { continue; } - wordsChars[j] = c; - String transformedWord = String.valueOf(wordsChars); - if (transformedWord.equals(endWord)) { + currentWordChars[j] = c; + String newWord = new String(currentWordChars); + + if (newWord.equals(endWord)) { return level + 1; } - if (set.contains(transformedWord)) { - set.remove(transformedWord); - queue.offer(transformedWord); + if (wordSet.remove(newWord)) { + queue.offer(newWord); } } - wordsChars[j] = originalChars; + currentWordChars[j] = originalChar; } } level++; diff --git a/src/test/java/com/thealgorithms/strings/WordLadderTest.java b/src/test/java/com/thealgorithms/strings/WordLadderTest.java index c59f2d8b..d933ebed 100644 --- a/src/test/java/com/thealgorithms/strings/WordLadderTest.java +++ b/src/test/java/com/thealgorithms/strings/WordLadderTest.java @@ -5,6 +5,8 @@ import static org.junit.jupiter.api.Assertions.assertEquals; import java.util.Arrays; import java.util.List; import org.junit.jupiter.api.Test; +import org.junit.jupiter.params.ParameterizedTest; +import org.junit.jupiter.params.provider.CsvSource; public class WordLadderTest { @@ -38,4 +40,12 @@ public class WordLadderTest { List wordList2 = Arrays.asList("hot", "dot", "dog", "lot", "log"); assertEquals(WordLadder.ladderLength("hit", "cog", wordList2), 0); } + + @ParameterizedTest + @CsvSource({"'a', 'c', 'b,c', 2", "'a', 'c', 'a', 0", "'a', 'a', 'a', 0", "'ab', 'cd', 'ad,bd,cd', 3", "'a', 'd', 'b,c,d', 2", "'a', 'd', 'b,c,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z,d', 2"}) + void testLadderLength(String beginWord, String endWord, String wordListStr, int expectedLength) { + List wordList = List.of(wordListStr.split(",")); + int result = WordLadder.ladderLength(beginWord, endWord, wordList); + assertEquals(expectedLength, result); + } }