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refactor: WordLadder (#5434)

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* refactor: WordLadder

* refactor: fix redundant check

---------

Co-authored-by: alxkm <alx@alx.com>
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Alex Klymenko 2024-08-30 09:49:55 +02:00 committed by GitHub
parent 87cf89192b
commit 14916e692f
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2 changed files with 34 additions and 54 deletions
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78
src/main/java/com/thealgorithms/strings/WordLadder.java
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@ -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<String> wordList) {
HashSet<String> set = new HashSet<>(wordList);
Set<String> 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++;

10
src/test/java/com/thealgorithms/strings/WordLadderTest.java
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@ -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<String> 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<String> wordList = List.of(wordListStr.split(","));
int result = WordLadder.ladderLength(beginWord, endWord, wordList);
assertEquals(expectedLength, result);
}
}