40 lines
1.3 KiB
Java
40 lines
1.3 KiB
Java
import java.util.*;
|
|
import java.util.stream.IntStream;
|
|
|
|
// https://en.wikipedia.org/wiki/Suffix_array
|
|
public class SuffixArray2 {
|
|
|
|
// suffix array in O(n*log^2(n))
|
|
public static int[] suffixArray(CharSequence s) {
|
|
int n = s.length();
|
|
Integer[] sa = IntStream.range(0, n).mapToObj(Integer::valueOf).toArray(Integer[]::new);
|
|
int[] rank = s.chars().toArray();
|
|
|
|
for (int len = 1; len < n; len *= 2) {
|
|
long[] rank2 = new long[n];
|
|
for (int i = 0; i < n; i++)
|
|
rank2[i] = ((long) rank[i] << 32) + (i + len < n ? rank[i + len] + 1 : 0);
|
|
|
|
Arrays.sort(sa, (a, b) -> Long.compare(rank2[a], rank2[b]));
|
|
|
|
for (int i = 0; i < n; i++)
|
|
rank[sa[i]] = i > 0 && rank2[sa[i - 1]] == rank2[sa[i]] ? rank[sa[i - 1]] : i;
|
|
}
|
|
return Arrays.stream(sa).mapToInt(Integer::intValue).toArray();
|
|
}
|
|
|
|
// random test
|
|
public static void main(String[] args) {
|
|
Random rnd = new Random(1);
|
|
for (int step = 0; step < 100000; step++) {
|
|
int n = rnd.nextInt(100);
|
|
StringBuilder s = rnd.ints(n, 0, 10).collect(StringBuilder::new, (sb, i) -> sb.append((char) ('\1' + i)), StringBuilder::append);
|
|
int[] sa = suffixArray(s);
|
|
for (int i = 0; i + 1 < n; i++)
|
|
if (s.substring(sa[i]).compareTo(s.substring(sa[i + 1])) >= 0)
|
|
throw new RuntimeException();
|
|
}
|
|
System.out.println("Test passed");
|
|
}
|
|
}
|