StringTransformation: fix & add Youtube link

Author: andrei-punko

README.md

@@ -221,6 +221,7 @@ they contain enough code which describes implementation in a natural way.
 | Подсчет единиц в бинарной записи числа (leetcode)                                                | [Youtube](https://youtu.be/F8zwvJYw0R8) | [Code](src/main/java/by/andd3dfx/numeric/CountOnesInBinaryForm.java)                                                                                                                |
 | Ревью кода из интервью #4 (LIVE)                                                                 | [Youtube](https://youtu.be/Y84nyje-U1c) | -                                                                                                                                                                                   |
 | Ревью кода из интервью #5 (LIVE)                                                                 | [Youtube](https://youtu.be/WT6wfFsNmxo) | -                                                                                                                                                                                   |
+| Проверка возможности получения одной строки из другой за одно изменение                          | [Youtube](https://youtu.be/GOSWr4jHng8) | [Code](src/main/java/by/andd3dfx/string/StringTransformation.java)                                                                                                                  |
 
 ## Materials & notes
 

src/main/java/by/andd3dfx/string/StringTransformation.java

@@ -2,26 +2,26 @@
 
 import org.apache.commons.lang3.StringUtils;
 
-import static org.apache.commons.lang3.StringUtils.substring;
-
 /**
+ * <pre>
  * Написать метод (класс и импорты не нужны) на вход которого приходит две строки.
  * На выходе надо проверить можно ли получить одну строку из другой за 1 исправление:
  * - замена одного символа в одной строке
  * - вставка/удаление одного символа из одной строки
- * <p>
+ *
  * Примеры тестовых сценариев:
  * first = "a", second = "b" -> true
  * first = "ab", second = "b" -> true
  * first = "ab", second = "cb" -> true
  * first = "ab", second = "ba" -> false
  * first = "abcd", second = "abd" -> true
+ * </pre>
  */
 public class StringTransformation {
 
     public static boolean couldTransform(String first, String second) {
-        var s1 = first.toCharArray();
-        var s2 = second.toCharArray();
+        char[] s1 = first.toCharArray();
+        char[] s2 = second.toCharArray();
 
         var len1 = s1.length;
         var len2 = s2.length;
@@ -43,25 +43,26 @@ public static boolean couldTransform(String first, String second) {
             return true;
         }
 
-        // Lengths differ by 1 - need to remove/add one character
+        // Lengths differ by 1 - so need to remove/add one character
         var pos = 0;
         while (pos < len1 && pos < len2 && s1[pos] == s2[pos]) {
             pos++;
         }
 
-        if (pos + 1 < len1 && s1[pos + 1] == s2[pos]) {
+        if (pos + 1 < len1 && pos < len2 && s1[pos + 1] == s2[pos]) {
             return remainingPartsShouldBeEqual(first, pos + 1, second, pos);
         }
-        if (pos + 1 < len2 && s1[pos] == s2[pos + 1]) {
+        if (pos < len1 && pos + 1 < len2 && s1[pos] == s2[pos + 1]) {
             return remainingPartsShouldBeEqual(first, pos, second, pos + 1);
         }
+
         return true;
     }
 
     private static boolean remainingPartsShouldBeEqual(String first, int from1, String second, int from2) {
         return StringUtils.equals(
-                substring(first, from1),
-                substring(second, from2)
+                first.substring(from1),
+                second.substring(from2)
         );
     }
 }

src/test/java/by/andd3dfx/string/StringTransformationTest.java

@@ -16,21 +16,21 @@ public void couldTransform_changeOneChar() {
 
     @Test
     public void couldTransform_removeOneChar() {
-        assertThat(couldTransform("abcd", "abc")).isTrue(); // remove one (last) char
         assertThat(couldTransform("abcd", "bcd")).isTrue(); // remove one (first) char
-        assertThat(couldTransform("abcd", "abd")).isTrue(); // remove one (inner) char
+        assertThat(couldTransform("abcd", "acd")).isTrue(); // remove one (inner) char
+        assertThat(couldTransform("abcd", "abc")).isTrue(); // remove one (last) char
     }
 
     @Test
     public void couldTransform_addOneChar() {
-        assertThat(couldTransform("abc", "abcd")).isTrue(); // add one (last) char
         assertThat(couldTransform("bcd", "abcd")).isTrue(); // add one (first) char
         assertThat(couldTransform("abd", "abcd")).isTrue(); // add one (inner) char
+        assertThat(couldTransform("abc", "abcd")).isTrue(); // add one (last) char
     }
 
     @Test
     public void couldTransform_significantlyDifferentLengths() {
-        assertThat(couldTransform("abcd", "bc")).isFalse();
+        assertThat(couldTransform("abcd", "ab")).isFalse();
         assertThat(couldTransform("bc", "abcd")).isFalse();
     }
 
@@ -40,4 +40,4 @@ public void couldTransform_transformIsNotPossible() {
         assertThat(couldTransform("abcde", "abdm")).isFalse();  // different lengths
         assertThat(couldTransform("abdm", "abcde")).isFalse();  // different lengths
     }
-}
+}