Second jump search

src/phonebook/Contact.java

@@ -0,0 +1,20 @@
+package phonebook;
+
+public class Contact {
+
+  private final String number;
+  private final String name;
+
+  public Contact(String number, String name) {
+    this.number = number;
+    this.name = name;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public String getNumber() {
+    return number;
+  }
+}

src/phonebook/Main.java

@@ -1,7 +1,79 @@
 package phonebook;
 
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
 public class Main {
-    public static void main(String[] args) {
-        System.out.print("Hello world!");
+
+  private static final String CONTACT_DATA_DIRECTORY = "data/directory.txt";
+  private static final String FIND_REQUESTS_DIRECTORY = "data/find.txt";
+
+  public static void main(String[] args) throws IOException {
+    List<Contact> contacts = parseContacts();
+    bubbleSort(contacts);
+
+    List<String> requests = Files.readAllLines(Paths.get(FIND_REQUESTS_DIRECTORY));
+
+    long start = System.currentTimeMillis();
+    int cnt = 1;
+    for (String request : requests) {
+      Optional<Contact> contact = search(contacts, request);
+      if (contact.isPresent()) {
+        System.out.printf("%d. %s has number %s\n", cnt++, request, contact.get().getNumber());
+      }
     }
+    System.out.printf("To find all entries it taken %d ms\n", System.currentTimeMillis() - start);
+  }
+
+  private static Optional<Contact> search(List<Contact> contacts, String name) {
+    int sqr = (int) Math.sqrt(contacts.size());
+    int lo = 0, hi = Math.min(sqr, contacts.size() - 1);
+    while (lo < hi) {
+      Contact contact = contacts.get(hi);
+      int comparation = Objects.compare(contact.getName(), name, Comparator.naturalOrder());
+      if (comparation == 0) {
+        return Optional.of(contact);
+      } else if (comparation < 0) {
+        lo = hi + 1;
+        hi = Math.min(hi + sqr + 1, contacts.size() - 1);
+      } else {
+        for (int i = hi; i >= lo; i--) {
+          Contact current = contacts.get(i);
+          if (Objects.equals(current.getName(), name)) {
+            return Optional.of(contact);
+          }
+        }
+        return Optional.empty();
+      }
+    }
+    return Optional.empty();
+  }
+
+  private static void bubbleSort(List<Contact> contacts) {
+    for (int i = 0; i < contacts.size(); i++) {
+      for (int j = contacts.size() - 1; j > i; j--) {
+        int comparing = Objects.compare(contacts.get(j), contacts.get(j - 1),
+            Comparator.comparing(Contact::getName));
+        if (comparing < 0) {
+          Collections.swap(contacts, j, j - 1);
+        }
+      }
+    }
+  }
+
+  private static List<Contact> parseContacts() throws IOException {
+    Stream<String> directoryLines = Files.lines(Paths.get(CONTACT_DATA_DIRECTORY));
+    return directoryLines.map(line -> new Contact(line.substring(0, line.indexOf(" ")),
+        line.substring(line.indexOf(" ") + 1)))
+        .collect(Collectors.toCollection(ArrayList::new));
+  }
 }