added finite state machine to calculate the number of ones and zeros in a binary string

src/main/kotlin/other/BinaryDigitsCounter.kt

@@ -0,0 +1,62 @@
+package other
+
+/**
+ * This algorithm counts the number of ones and zeros in a binary string
+ * and implemented on a finite state machine
+ *
+ */
+class BinaryDigitsCounter {
+
+    /**
+     * Stores the result of the algorithm
+     *
+     */
+    data class Result(private val ones: Int = 0, private val zeros: Int = 0)
+
+    /**
+     * Represents two states
+     *
+     */
+    private enum class State {
+        ONE, ZERO
+    }
+
+    fun compute(binaryString: String): Result { // 1010010011
+        if (binaryString.isEmpty()) {
+            return Result()
+        }
+
+        // define initial state
+        var currentState = if (binaryString.first() == '1') State.ONE else State.ZERO
+
+        var onesCount = 0
+        var zerosCount = 0
+
+        binaryString.forEach { symbol ->
+            // we use 'when' statement to toggle the state
+            when (currentState) {
+                State.ONE -> {
+                    if (symbol == '0') {
+                        zerosCount++
+                        // move to another state
+                        currentState = State.ZERO
+                    } else {
+                        onesCount++
+                    }
+                }
+                State.ZERO -> {
+                    if (symbol == '1') {
+                        onesCount++
+                        // move to another state
+                        currentState = State.ONE
+                    } else {
+                        zerosCount++
+                    }
+                }
+            }
+        }
+
+        return Result(onesCount, zerosCount)
+    }
+
+}

src/test/kotlin/other/BinaryDigitsCounterTest.kt

@@ -0,0 +1,45 @@
+package other
+
+import org.junit.Test
+import org.junit.jupiter.api.Assertions
+
+internal class BinaryDigitsCounterTest {
+
+    private val counter = BinaryDigitsCounter()
+
+    @Test
+    fun test_empty_string() {
+        val result = counter.compute("")
+
+        Assertions.assertEquals(BinaryDigitsCounter.Result(), result)
+    }
+
+    @Test
+    fun test_binary_string_1() {
+        val result = counter.compute("10101111000")
+
+        Assertions.assertEquals(BinaryDigitsCounter.Result(6, 5), result)
+    }
+
+    @Test
+    fun test_binary_string_2() {
+        val result = counter.compute("0100000111110010101010")
+
+        Assertions.assertEquals(BinaryDigitsCounter.Result(10, 12), result)
+    }
+
+    @Test
+    fun test_binary_string_3() {
+        val result = counter.compute("1111111111")
+
+        Assertions.assertEquals(BinaryDigitsCounter.Result(10, 0), result)
+    }
+
+    @Test
+    fun test_binary_string_4() {
+        val result = counter.compute("0000000000")
+
+        Assertions.assertEquals(BinaryDigitsCounter.Result(0, 10), result)
+    }
+
+}