JAVA:实现字符串WordLadder字梯算法(附完整源码)

package com.thealgorithms.strings;

import java.util.List;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
import java.util.HashSet;


class WordLadder {

    /**
     * Driver Code
     */
    public static void main(String[] args) {

        String beginWord = "hit";
        String endWord = "cog";
        String words[] = {"hot", "dot", "dog", "lot", "log", "cog"};
        List<String> wordList = Arrays.asList(words);

        System.out.println("Ladder Length: " + ladderLength(beginWord, endWord, wordList));
    }


    public static int ladderLength(String beginWord, String endWord, List<String> wordList) {
        HashSet<String> set = new HashSet();
        for (String word : wordList) {
            set.add(word);
        }

        if (!set.contains(endWord)) {
            return 0;
        }

        Queue<String> queue = new LinkedList();
        queue.offer(beginWord);
        int level = 1;

        while (!queue.isEmpty()) {
            int size = queue.size();
            for (int i = 0; i < size; i++) {
                String curr = queue.poll();
                char[] words_chars = curr.toCharArray();
                for (int j = 0; j < words_chars.length; j++) {
                    char original_chars = words_chars[j];
                    for (char c = 'a'; c <= 'z'; c++) {
                        if (words_chars[j] == c) {
                            continue;
                        }
                        words_chars[j] = c;
                        String new_word = String.valueOf(words_chars);
                        if (new_word.equals(endWord)) {
                            return level + 1;
                        }
                        if (set.contains(new_word)) {
                            set.remove(new_word);
                            queue.offer(new_word);
                        }
                    }
                    words_chars[j] = original_chars;
                }
            }
            level++;
        }
        return 0;
    }
}

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