Added Jump Search (examplehub#57)

realDuYuanChao · github-actions · web-flow · commit 3fbd93dc9f48 · 2020-11-24T15:04:47.000+08:00
* add jump search

* Formatted with Google Java Formatter

Co-authored-by: github-actions &lt;${GITHUB_ACTOR}@users.noreply.github.com&gt;
diff --git a/src/main/java/com/examplehub/maths/SumOfFactorial.java b/src/main/java/com/examplehub/maths/SumOfFactorial.java
@@ -0,0 +1,16 @@
+package com.examplehub.maths;
+
+/** Calculate 1! + 2! + 3! + ... n! */
+public class SumOfFactorial {
+  public static int sum(int n) {
+    return sum(1, n);
+  }
+
+  public static int sum(int i, int n) {
+    if (i == n) {
+      return n;
+    } else {
+      return i + i * sum(i + 1, n);
+    }
+  }
+}
diff --git a/src/main/java/com/examplehub/searches/JumpSearch.java b/src/main/java/com/examplehub/searches/JumpSearch.java
@@ -0,0 +1,32 @@
+package com.examplehub.searches;
+
+public class JumpSearch implements Search {
+  @Override
+  public int search(int[] numbers, int key) {
+    int length = numbers.length;
+    int steps = (int) Math.floor(Math.sqrt(length));
+    int prev = 0;
+    while (numbers[Math.min(steps, length) - 1] < key) {
+      prev = steps;
+      steps += (int) Math.floor(Math.sqrt(length));
+      if (prev >= length) {
+        return -1;
+      }
+    }
+    while (numbers[prev] < key) {
+      prev++;
+      if (prev == Math.min(steps, length)) {
+        return -1;
+      }
+    }
+    if (numbers[prev] == key) {
+      return prev;
+    }
+    return -1;
+  }
+
+  @Override
+  public <T extends Comparable<T>> int search(T[] array, T key) {
+    return 0;
+  }
+}
diff --git a/src/test/java/com/examplehub/maths/SumOfFactorialTest.java b/src/test/java/com/examplehub/maths/SumOfFactorialTest.java
@@ -0,0 +1,16 @@
+package com.examplehub.maths;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class SumOfFactorialTest {
+  @Test
+  void testSum() {
+    assertEquals(1, SumOfFactorial.sum(1));
+    assertEquals(3, SumOfFactorial.sum(2));
+    assertEquals(9, SumOfFactorial.sum(3));
+    assertEquals(33, SumOfFactorial.sum(4));
+    assertEquals(153, SumOfFactorial.sum(5));
+  }
+}
diff --git a/src/test/java/com/examplehub/searches/JumpSearchTest.java b/src/test/java/com/examplehub/searches/JumpSearchTest.java
@@ -0,0 +1,27 @@
+package com.examplehub.searches;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.stream.IntStream;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class JumpSearchTest {
+  private Search search;
+
+  @BeforeEach
+  void setup() {
+    search = new JumpSearch();
+  }
+
+  @Test
+  void testLinearSearch() {
+    int[] ints = IntStream.range(0, 10).toArray();
+    for (int i = 0; i < ints.length; ++i) {
+      assertEquals(i, search.search(ints, i));
+    }
+    assertEquals(-1, search.search(ints, 10));
+    assertEquals(-1, search.search(ints, 100));
+    assertEquals(-1, search.search(ints, -1));
+  }
+}
