Merge pull request #11 from harry0000/z-algorithm

Add Z algorithm

.github/workflows/ci.yaml

@@ -8,11 +8,11 @@ jobs:
       fail-fast: false
       matrix:
         name: [ "test" ]
-        scala: [ 3.3.0, 3.3.1 ]
+        scala: [ 3.3.0, 3.4.1 ]
         java: [ 20, 21 ]
         include:
           - name: "format"
-            scala: 3.3.1
+            scala: 3.4.1
             java: 21
         exclude:
           - name: "test"

build.sbt

@@ -1,4 +1,4 @@
-lazy val supportedScalaVersions = List("3.3.1", "3.3.0")
+lazy val supportedScalaVersions = List("3.4.1", "3.3.0")
 
 lazy val root = project
   .in(file("."))
@@ -16,6 +16,6 @@ lazy val root = project
       "-unchecked",
       "-Wunused:all"
     ),
-    libraryDependencies += "org.scalameta" %% "munit" % "0.7.29" % Test,
+    libraryDependencies += "org.scalameta" %% "munit" % "1.0.0-M11" % Test,
     Test / parallelExecution := false
   )

src/main/scala/io/github/acl4s/ModInt.scala

@@ -90,8 +90,7 @@ object Modulus {
   inline def apply[T <: Int](): Modulus[T] = Mod(compiletime.constValue[T])
 }
 
-final case class StaticModInt[T <: Int] private (private[this] var _value: Int)(using m: Modulus[T])
-    extends ModIntBase[T] {
+final case class StaticModInt[T <: Int] private (private var _value: Int)(using m: Modulus[T]) extends ModIntBase[T] {
   override type Self = StaticModInt[T]
   override val mod: T = m.value
 
@@ -204,7 +203,7 @@ object ModInt998244353 {
   def apply(value: Long): ModInt998244353 = StaticModInt(value)
 }
 
-final case class DynamicModInt private (private[this] var _value: Int) extends ModIntBase[Int] {
+final case class DynamicModInt private (private var _value: Int) extends ModIntBase[Int] {
   override type Self = DynamicModInt
   override val mod: Int = DynamicModInt.bt.m
 

src/main/scala/io/github/acl4s/String.scala

@@ -0,0 +1,34 @@
+package io.github.acl4s
+
+import scala.reflect.ClassTag
+
+/**
+ * Reference:
+ * D. Gusfield,
+ * Algorithms on Strings, Trees, and Sequences: Computer Science and
+ * Computational Biology
+ */
+private[acl4s] def zAlgorithmImpl[T: ClassTag](s: Array[T]): Array[Int] = {
+  val n = s.length
+  if (n == 0) {
+    return Array.empty
+  }
+  val z = new Array[Int](n)
+  z(0) = 0
+  var j = 0
+  for (i <- 1 until n) {
+    var k = if (j + z(j) <= i) { 0 }
+    else { Math.min(j + z(j) - i, z(i - j)) }
+    while (i + k < n && s(k) == s(i + k)) {
+      k += 1
+    }
+    z(i) = k
+    if (j + z(j) < i + z(i)) {
+      j = i
+    }
+  }
+  z(0) = n
+  z
+}
+
+def zAlgorithm(s: String): Array[Int] = zAlgorithmImpl(s.toCharArray)

src/main/scala/io/github/acl4s/TwoSAT.scala

@@ -1,5 +1,7 @@
 package io.github.acl4s
 
+import scala.util.boundary, boundary.break
+
 /**
  * Reference:
  * B. Aspvall, M. Plass, and R. Tarjan,
@@ -28,12 +30,12 @@ class TwoSAT(private val n: Int) {
 
   def satisfiable(): Boolean = {
     val (_, id) = scc.sccIds()
-    (0 until n).foreach(i => {
-      if (id(2 * i) == id(2 * i + 1)) {
-        return false
+    boundary {
+      for (i <- 0 until n) {
+        if (id(2 * i) == id(2 * i + 1)) { break(false) }
+        answer(i) = id(2 * i) < id(2 * i + 1)
       }
-      answer(i) = id(2 * i) < id(2 * i + 1)
-    })
-    true
+      true
+    }
   }
 }

src/test/scala/io/github/acl4s/StringSuite.scala

@@ -0,0 +1,20 @@
+package io.github.acl4s
+
+class StringSuite extends munit.FunSuite {
+
+  test("zAlgorithm") {
+    {
+      val str = "abracadabra";
+      val lcp = zAlgorithm(str)
+
+      assertEquals(lcp.toSeq, Seq(11, 0, 0, 1, 0, 1, 0, 4, 0, 0, 1))
+    }
+    {
+      val str = "ababababa"
+      val lcp = zAlgorithm(str)
+
+      assertEquals(lcp.toSeq, Seq(9, 0, 7, 0, 5, 0, 3, 0, 1))
+    }
+  }
+
+}