Add example of a linear search algorithm

anverbogatov · anverbogatov · commit 7317833944b6 · 2022-03-13T20:56:24.000+04:00
diff --git a/src/main/java/com/anverbogatov/algorithms/search/LinearSearch.java b/src/main/java/com/anverbogatov/algorithms/search/LinearSearch.java
@@ -0,0 +1,31 @@
+package com.anverbogatov.algorithms.search;
+
+/**
+ * This class shows simple implementation of a linear search algorithm.
+ */
+public final class LinearSearch {
+
+    public static final int NOT_FOUND = -1;
+
+    /**
+     * Search specific number in a given array of numbers using linear search algorithm.
+     * Linear search algorithm has O(n) complexity.
+     *
+     * @param numbers - given array of numbers in which search will be performed
+     * @param value   - given value that must be found in the array
+     * @return index of the value in provided array or '-1' if not found
+     */
+    public static int linearSearch(int[] numbers, int value) {
+        if (numbers.length == 0) {
+            return NOT_FOUND;
+        }
+
+        for (int i = 0; i < numbers.length; i++) {
+            var el = numbers[i];
+            if (el == value) {
+                return i;
+            }
+        }
+        return NOT_FOUND;
+    }
+}
diff --git a/src/test/java/com/anverbogatov/algorithms/search/LinearSearchTest.java b/src/test/java/com/anverbogatov/algorithms/search/LinearSearchTest.java
@@ -0,0 +1,50 @@
+package com.anverbogatov.algorithms.search;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.stream.IntStream;
+
+public class LinearSearchTest {
+
+    @Test
+    public void testLinearSearchWithEmptyArray() {
+        // given
+        var numbers = new int[]{};
+        // when
+        var index = LinearSearch.linearSearch(numbers, 0);
+        // then
+        Assert.assertEquals(-1, index);
+    }
+
+    @Test
+    public void testLinearSearchWithSingleElementArrayHappy() {
+        // given
+        var numbers = new int[]{47};
+        // when
+        var index = LinearSearch.linearSearch(numbers, 47);
+        // then
+        Assert.assertEquals(0, index);
+    }
+
+    @Test
+    public void testLinearSearchWithSingleElementArrayFailure() {
+        // given
+        var numbers = new int[]{47};
+        // when
+        var index = LinearSearch.linearSearch(numbers, 12);
+        // then
+        Assert.assertEquals(-1, index);
+    }
+
+    @Test
+    public void testLinearSearch() {
+        // given
+        var numbers = IntStream.range(1, 100).toArray();
+        var n = 21;
+        // when
+        var index = LinearSearch.linearSearch(numbers, n);
+        //then
+        Assert.assertEquals(20, index);
+    }
+}
