95 lines
3.2 KiB
Java
95 lines
3.2 KiB
Java
import java.io.IOException;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Map;
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import java.util.PriorityQueue;
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import java.util.Set;
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import java.util.stream.IntStream;
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public class WordLadder {
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private static int distance(String s1, String s2) {
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assert s1.length() == s2.length();
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return (int) IntStream.range(0, s1.length())
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.filter(i -> s1.charAt(i) != s2.charAt(i))
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.count();
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}
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private static void wordLadder(Map<Integer, Set<String>> words, String fw, String tw) {
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wordLadder(words, fw, tw, 8);
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}
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private static void wordLadder(Map<Integer, Set<String>> words, String fw, String tw, int limit) {
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if (fw.length() != tw.length()) {
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throw new IllegalArgumentException("From word and to word must have the same length");
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}
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Set<String> ws = words.get(fw.length());
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if (ws.contains(fw)) {
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List<String> primeList = new ArrayList<>();
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primeList.add(fw);
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PriorityQueue<List<String>> queue = new PriorityQueue<>((chain1, chain2) -> {
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int cmp1 = Integer.compare(chain1.size(), chain2.size());
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if (cmp1 == 0) {
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String last1 = chain1.get(chain1.size() - 1);
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int d1 = distance(last1, tw);
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String last2 = chain2.get(chain2.size() - 1);
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int d2 = distance(last2, tw);
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return Integer.compare(d1, d2);
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}
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return cmp1;
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});
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queue.add(primeList);
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while (queue.size() > 0) {
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List<String> curr = queue.remove();
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if (curr.size() > limit) {
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continue;
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}
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String last = curr.get(curr.size() - 1);
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for (String word : ws) {
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if (distance(last, word) == 1) {
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if (word.equals(tw)) {
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curr.add(word);
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System.out.println(String.join(" -> ", curr));
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return;
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}
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if (!curr.contains(word)) {
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List<String> cp = new ArrayList<>(curr);
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cp.add(word);
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queue.add(cp);
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}
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}
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}
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}
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}
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System.err.printf("Cannot turn `%s` into `%s`%n", fw, tw);
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}
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public static void main(String[] args) throws IOException {
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Map<Integer, Set<String>> words = new HashMap<>();
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for (String line : Files.readAllLines(Path.of("unixdict.txt"))) {
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Set<String> wl = words.computeIfAbsent(line.length(), HashSet::new);
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wl.add(line);
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}
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wordLadder(words, "boy", "man");
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wordLadder(words, "girl", "lady");
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wordLadder(words, "john", "jane");
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wordLadder(words, "child", "adult");
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wordLadder(words, "cat", "dog");
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wordLadder(words, "lead", "gold");
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wordLadder(words, "white", "black");
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wordLadder(words, "bubble", "tickle", 12);
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}
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}
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