BAEL-7555-count-unique-digit-in-integer (#15933)

* BAEL-7555-count-unique-digit-in-integer

* rename test case

* add solution using stream

algorithms-modules/algorithms-miscellaneous-7/src/main/java/com/baeldung/algorithms/uniquedigit/UniqueDigitCounter.java

@@ -0,0 +1,36 @@
+package com.baeldung.algorithms.uniquedigit;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class UniqueDigitCounter {
+
+    public static int countWithSet(int number) {
+        number = Math.abs(number);
+        Set<Character> uniqueDigits = new HashSet<>();
+        String numberStr = String.valueOf(number);
+        for (char digit : numberStr.toCharArray()) {
+            uniqueDigits.add(digit);
+        }
+        return uniqueDigits.size();
+    }
+
+    public static int countWithBitManipulation(int number) {
+        if (number == 0) {
+            return 1;
+        }
+        number = Math.abs(number);
+        int mask = 0;
+        while (number > 0) {
+            int digit = number % 10;
+            mask |= 1 << digit;
+            number /= 10;
+        }
+        return Integer.bitCount(mask);
+    }
+
+    public static long countWithStreamApi(int number) {
+        return String.valueOf(Math.abs(number)).chars().distinct().count();
+    }
+
+}

algorithms-modules/algorithms-miscellaneous-7/src/test/java/com/baeldung/algorithms/uniquedigit/UniqueDigitCounterUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.algorithms.uniquedigit;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class UniqueDigitCounterUnitTest {
+
+    @Test
+    public void givenNotNegativeNumber_whenCountUniqueDigits_thenCorrectCount() {
+        assertEquals(3, UniqueDigitCounter.countWithSet(122333));
+        assertEquals(1, UniqueDigitCounter.countWithSet(0));
+        assertEquals(2, UniqueDigitCounter.countWithSet(101));
+
+        assertEquals(3, UniqueDigitCounter.countWithBitManipulation(122333));
+        assertEquals(1, UniqueDigitCounter.countWithBitManipulation(0));
+        assertEquals(2, UniqueDigitCounter.countWithBitManipulation(101));
+
+        assertEquals(3, UniqueDigitCounter.countWithStreamApi(122333));
+        assertEquals(1, UniqueDigitCounter.countWithStreamApi(0));
+        assertEquals(2, UniqueDigitCounter.countWithStreamApi(101));
+    }
+
+    @Test
+    public void givenNegativeNumber_whenCountUniqueDigits_thenCorrectCount() {
+        assertEquals(3, UniqueDigitCounter.countWithSet(-122333));
+        assertEquals(3, UniqueDigitCounter.countWithBitManipulation(-122333));
+        assertEquals(3, UniqueDigitCounter.countWithStreamApi(-122333));
+    }
+
+    @Test
+    public void givenLargeNumber_whenCountUniqueDigits_thenCorrectCount() {
+        assertEquals(2, UniqueDigitCounter.countWithSet(1000000000));
+        assertEquals(2, UniqueDigitCounter.countWithBitManipulation(1000000000));
+        assertEquals(2, UniqueDigitCounter.countWithStreamApi(1000000000));
+    }
+
+}