update

java/src/SuffixAutomaton.java

@@ -4,7 +4,7 @@ public class SuffixAutomaton {
 
 	public static class State {
 		int length;
-		int link;
+		int suffLink;
 		int[] next = new int[128];
 
 		{
@@ -19,7 +19,7 @@ public static State[] buildSuffixAutomaton(String s) {
 		int n = s.length();
 		State[] st = new State[Math.max(2, 2 * n - 1)];
 		st[0] = new State();
-		st[0].link = -1;
+		st[0].suffLink = -1;
 		st[0].endpos = -1;
 		int last = 0;
 		int size = 1;
@@ -29,32 +29,32 @@ public static State[] buildSuffixAutomaton(String s) {
 			st[cur].length = st[last].length + 1;
 			st[cur].endpos = st[last].length;
 			int p;
-			for (p = last; p != -1 && st[p].next[c] == -1; p = st[p].link) {
+			for (p = last; p != -1 && st[p].next[c] == -1; p = st[p].suffLink) {
 				st[p].next[c] = cur;
 			}
 			if (p == -1) {
-				st[cur].link = 0;
+				st[cur].suffLink = 0;
 			} else {
 				int q = st[p].next[c];
 				if (st[p].length + 1 == st[q].length)
-					st[cur].link = q;
+					st[cur].suffLink = q;
 				else {
 					int clone = size++;
 					st[clone] = new State();
 					st[clone].length = st[p].length + 1;
 					st[clone].next = st[q].next.clone();
-					st[clone].link = st[q].link;
-					for (; p != -1 && st[p].next[c] == q; p = st[p].link)
+					st[clone].suffLink = st[q].suffLink;
+					for (; p != -1 && st[p].next[c] == q; p = st[p].suffLink)
 						st[p].next[c] = clone;
-					st[q].link = clone;
-					st[cur].link = clone;
+					st[q].suffLink = clone;
+					st[cur].suffLink = clone;
 					st[clone].endpos = -1;
 				}
 			}
 			last = cur;
 		}
 		for (int i = 1; i < size; i++) {
-			st[st[i].link].ilink.add(i);
+			st[st[i].suffLink].ilink.add(i);
 		}
 		return Arrays.copyOf(st, size);
 	}
@@ -63,14 +63,20 @@ public static State[] buildSuffixAutomaton(String s) {
 	public static void main(String[] args) {
 		Random rnd = new Random(1);
 		for (int step = 0; step < 100_000; step++) {
-			int n1 = rnd.nextInt(10);
-			int n2 = rnd.nextInt(10);
-			String s1 = getRandomString(n1, rnd);
-			String s2 = getRandomString(n2, rnd);
-			String res1 = lcs(s1, s2);
-			int res2 = slowLcs(s1, s2);
+			int n1 = rnd.nextInt(20);
+			int n2 = rnd.nextInt(20) + 1;
+			String a = getRandomString(n1, rnd);
+			String b = getRandomString(n2, rnd);
+			String res1 = lcs(a, b);
+			int res2 = slowLcs(a, b);
 			if (res1.length() != res2)
 				throw new RuntimeException();
+			Integer[] occurrences1 = occurrences(a, b);
+			List<Integer> occurrences2 = new ArrayList<>();
+			for (int p = a.indexOf(b); p != -1; p = a.indexOf(b, p + 1))
+				occurrences2.add(p);
+			if (!Arrays.equals(occurrences1, occurrences2.toArray(new Integer[occurrences2.size()])))
+				throw new RuntimeException();
 		}
 	}
 
@@ -85,7 +91,7 @@ static String lcs(String a, String b) {
 		for (int i = 0, cur = 0; i < b.length(); ++i) {
 			char c = b.charAt(i);
 			if (st[cur].next[c] == -1) {
-				for (; cur != -1 && st[cur].next[c] == -1; cur = st[cur].link) {
+				for (; cur != -1 && st[cur].next[c] == -1; cur = st[cur].suffLink) {
 				}
 				if (cur == -1) {
 					cur = 0;
@@ -105,24 +111,21 @@ static String lcs(String a, String b) {
 		return b.substring(bestPos - bestLen + 1, bestPos + 1);
 	}
 
-	static int[] occurrences(String haystack, String needle) {
+	static Integer[] occurrences(String haystack, String needle) {
 		String common = lcs(haystack, needle);
 		if (!common.equals(needle))
-			return new int[0];
+			return new Integer[0];
 		List<Integer> list = new ArrayList<>();
-		dfs(buildSuffixAutomaton(haystack), bestState, needle.length(), list);
-		int[] res = new int[list.size()];
-		for (int i = 0; i < res.length; i++)
-			res[i] = list.get(i);
-		Arrays.sort(res);
-		return res;
+		occurrencesDfs(buildSuffixAutomaton(haystack), bestState, needle.length(), list);
+		Collections.sort(list);
+		return list.toArray(new Integer[list.size()]);
 	}
 
-	static void dfs(State[] st, int p, int len, List<Integer> list) {
+	static void occurrencesDfs(State[] st, int p, int len, List<Integer> list) {
 		if (st[p].endpos != -1 || p == 0)
 			list.add(st[p].endpos - len + 1);
 		for (int x : st[p].ilink)
-			dfs(st, x, len, list);
+			occurrencesDfs(st, x, len, list);
 	}
 
 	static int slowLcs(String a, String b) {