From 734f7a4a042f68d4bc4fd8dd83ae6227f432a297 Mon Sep 17 00:00:00 2001
From: sangin-lee <92197656+sangin-lee@users.noreply.github.com>
Date: Sun, 12 Dec 2021 01:54:12 +0900
Subject: [PATCH] Add Array Left Rotation (#2869)

---
 .../others/ArrayLeftRotation.java             | 33 +++++++++++++
 .../others/ArrayLeftRotationTest.java         | 48 +++++++++++++++++++
 2 files changed, 81 insertions(+)
 create mode 100644 src/main/java/com/thealgorithms/others/ArrayLeftRotation.java
 create mode 100644 src/test/java/com/thealgorithms/others/ArrayLeftRotationTest.java

diff --git a/src/main/java/com/thealgorithms/others/ArrayLeftRotation.java b/src/main/java/com/thealgorithms/others/ArrayLeftRotation.java
new file mode 100644
index 00000000..e1dfa35f
--- /dev/null
+++ b/src/main/java/com/thealgorithms/others/ArrayLeftRotation.java
@@ -0,0 +1,33 @@
+package com.thealgorithms.others;
+
+/*
+ * A left rotation operation on an array
+ * shifts each of the array's elements
+ * given integer n unit to the left.
+ * 
+ * @author sangin-lee 
+ */
+
+public class ArrayLeftRotation {
+
+	/*
+	 * Returns the result of left rotation of given array arr and integer n
+	 * 
+	 * @param arr : int[] given array
+	 * 
+	 * @param n : int given integer
+	 * 
+	 * @return : int[] result of left rotation
+	 */
+	public static int[] rotateLeft(int[] arr, int n) {
+		int size = arr.length;
+		int[] dst = new int[size];
+		n = n % size;
+		for(int i = 0; i < size; i++) {
+			dst[i] = arr[n];
+			n = (n + 1) % size;
+		}
+		return dst;
+	}
+
+}
diff --git a/src/test/java/com/thealgorithms/others/ArrayLeftRotationTest.java b/src/test/java/com/thealgorithms/others/ArrayLeftRotationTest.java
new file mode 100644
index 00000000..2efebb08
--- /dev/null
+++ b/src/test/java/com/thealgorithms/others/ArrayLeftRotationTest.java
@@ -0,0 +1,48 @@
+package com.thealgorithms.others;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ArrayLeftRotationTest {
+
+	@Test
+	void testForOneElement() {
+		int[] arr = {3};
+		int[] result = ArrayLeftRotation.rotateLeft(arr, 3);
+		assertArrayEquals(arr, result);
+	}
+	
+	@Test
+	void testForZeroStep() {
+		int[] arr = {3, 1, 5, 8, 6};
+		int[] result = ArrayLeftRotation.rotateLeft(arr, 0);
+		assertArrayEquals(arr, result);
+	}
+	
+	@Test
+	void testForEqualSizeStep() {
+		int[] arr = {3, 1, 5, 8, 6};
+		int[] result = ArrayLeftRotation.rotateLeft(arr, 5);
+		assertArrayEquals(arr, result);
+	}
+	
+	@Test
+	void testForLowerSizeStep() {
+		int[] arr = {3, 1, 5, 8, 6};
+		int n = 2;
+		int[] expected = {5, 8, 6, 3, 1};
+		int[] result = ArrayLeftRotation.rotateLeft(arr, n);
+		assertArrayEquals(expected, result);
+	}
+	
+	@Test
+	void testForHigherSizeStep() {
+		int[] arr = {3, 1, 5, 8, 6};
+		int n = 7;
+		int[] expected = {5, 8, 6, 3, 1};
+		int[] result = ArrayLeftRotation.rotateLeft(arr, n);
+		assertArrayEquals(expected, result);
+	}
+
+}