MissingNumber: adjust naming & solution. Add YT link

Author: andrei-punko

src/main/java/by/andd3dfx/numeric/MissingNumber.java

@@ -24,10 +24,12 @@
  * Explanation:
  * n = 9 since there are 9 numbers, so all numbers are in the range [0,9]. 8 is the missing number in the range since it does not appear in nums.
  * </pre>
+ *
+ * @see <a href="https://youtu.be/JGqssodAKJM">Video solution</a>
  */
 public class MissingNumber {
 
-    public int missingNumber(int[] nums) {
+    public int find_On_memory(int[] nums) {
         var n = nums.length;
         var flags = new boolean[n + 1];
         for (var num : nums) {
@@ -38,22 +40,24 @@ public int missingNumber(int[] nums) {
                 return i;
             }
         }
-        return -1;
+        throw new IllegalStateException();
     }
 
-    public int missingNumber2(int[] nums) {
+    public int find_O1_memory(int[] nums) {
         var n = nums.length;
         for (var i = 0; i < n; i++) {
-            var num = Math.abs(nums[i]);
-            if (num < n) {
-                nums[num] = -nums[num];
+            var index = Math.abs(nums[i]);
+            if (index < n) {
+                nums[index] = -nums[index];
             }
         }
+
         for (var i = 0; i < n; i++) {
             if (nums[i] > 0) {
                 return i;
             }
         }
+
         return n;
     }
 }

src/test/java/by/andd3dfx/numeric/MissingNumberTest.java

@@ -2,23 +2,29 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import org.junit.Before;
 import org.junit.Test;
 
 public class MissingNumberTest {
 
-    private final MissingNumber missingNumber = new MissingNumber();
+    private MissingNumber missingNumber;
+
+    @Before
+    public void setUp() throws Exception {
+        missingNumber = new MissingNumber();
+    }
 
     @Test
-    public void testMissingNumber() {
-        assertThat(missingNumber.missingNumber(new int[]{3, 0, 1})).isEqualTo(2);
-        assertThat(missingNumber.missingNumber(new int[]{0, 1})).isEqualTo(2);
-        assertThat(missingNumber.missingNumber(new int[]{9, 6, 4, 2, 3, 5, 7, 0, 1})).isEqualTo(8);
+    public void find_On_memory() {
+        assertThat(missingNumber.find_On_memory(new int[]{3, 0, 1})).isEqualTo(2);
+        assertThat(missingNumber.find_On_memory(new int[]{0, 1})).isEqualTo(2);
+        assertThat(missingNumber.find_On_memory(new int[]{9, 6, 4, 2, 3, 5, 7, 0, 1})).isEqualTo(8);
     }
 
     @Test
-    public void testMissingNumber2() {
-        assertThat(missingNumber.missingNumber2(new int[]{3, 0, 1})).isEqualTo(2);
-        assertThat(missingNumber.missingNumber2(new int[]{0, 1})).isEqualTo(2);
-        assertThat(missingNumber.missingNumber2(new int[]{9, 6, 4, 2, 3, 5, 7, 0, 1})).isEqualTo(8);
+    public void find_O1_memory() {
+        assertThat(missingNumber.find_O1_memory(new int[]{3, 0, 1})).isEqualTo(2);
+        assertThat(missingNumber.find_O1_memory(new int[]{0, 1})).isEqualTo(2);
+        assertThat(missingNumber.find_O1_memory(new int[]{9, 6, 4, 2, 3, 5, 7, 0, 1})).isEqualTo(8);
     }
 }