Add digit separation for large integers (#5543)

src/main/java/com/thealgorithms/greedyalgorithms/DigitSeparation.java

@@ -0,0 +1,40 @@
+package com.thealgorithms.greedyalgorithms;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * This class provides methods to separate the digits of a large positive number into a list.
+ */
+public class DigitSeparation {
+    public DigitSeparation() {
+    }
+    /**
+     * Separates the digits of a large positive number into a list in reverse order.
+     * @param largeNumber The large number to separate digits from.
+     * @return A list of digits in reverse order.
+     */
+    public List<Long> digitSeparationReverseOrder(long largeNumber) {
+        List<Long> result = new ArrayList<>();
+        if (largeNumber != 0) {
+            while (largeNumber != 0) {
+                result.add(Math.abs(largeNumber % 10));
+                largeNumber = largeNumber / 10;
+            }
+        } else {
+            result.add(0L);
+        }
+        return result;
+    }
+    /**
+     * Separates the digits of a large positive number into a list in forward order.
+     * @param largeNumber The large number to separate digits from.
+     * @return A list of digits in forward order.
+     */
+    public List<Long> digitSeparationForwardOrder(long largeNumber) {
+        List<Long> result = this.digitSeparationReverseOrder(largeNumber);
+        Collections.reverse(result);
+        return result;
+    }
+}

src/test/java/com/thealgorithms/greedyalgorithms/DigitSeparationTest.java

@@ -0,0 +1,78 @@
+package com.thealgorithms.greedyalgorithms;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.List;
+import org.junit.jupiter.api.Test;
+public class DigitSeparationTest {
+
+    @Test
+    public void testDigitSeparationReverseOrderSingleDigit() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationReverseOrder(5);
+        assertEquals(List.of(5L), result);
+    }
+
+    @Test
+    public void testDigitSeparationReverseOrderMultipleDigits() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationReverseOrder(123);
+        assertEquals(List.of(3L, 2L, 1L), result);
+    }
+
+    @Test
+    public void testDigitSeparationReverseOrderLargeNumber() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationReverseOrder(123456789);
+        assertEquals(List.of(9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L), result);
+    }
+
+    @Test
+    public void testDigitSeparationReverseOrderZero() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationReverseOrder(0);
+        assertEquals(List.of(0L), result);
+    }
+
+    @Test
+    public void testDigitSeparationReverseOrderNegativeNumbers() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationReverseOrder(-123);
+        assertEquals(List.of(3L, 2L, 1L), result);
+    }
+
+    @Test
+    public void testDigitSeparationForwardOrderSingleDigit() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationForwardOrder(5);
+        assertEquals(List.of(5L), result);
+    }
+
+    @Test
+    public void testDigitSeparationForwardOrderMultipleDigits() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationForwardOrder(123);
+        assertEquals(List.of(1L, 2L, 3L), result);
+    }
+
+    @Test
+    public void testDigitSeparationForwardOrderLargeNumber() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationForwardOrder(123456789);
+        assertEquals(List.of(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L), result);
+    }
+
+    @Test
+    public void testDigitSeparationForwardOrderZero() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationForwardOrder(0);
+        assertEquals(List.of(0L), result);
+    }
+
+    @Test
+    public void testDigitSeparationForwardOrderNegativeNumber() {
+        DigitSeparation digitSeparation = new DigitSeparation();
+        List<Long> result = digitSeparation.digitSeparationForwardOrder(-123);
+        assertEquals(List.of(1L, 2L, 3L), result);
+    }
+}