Improved solution to "Rotate String" problem

src/main/java/com/github/dkoval/leetcode/challenge/RotateString.java

@@ -40,4 +40,26 @@ public boolean rotateString(String s, String goal) {
             return false;
         }
     }
+
+    class RotateStringRev2 implements RotateString {
+
+        @Override
+        public boolean rotateString(String s, String goal) {
+            int n = s.length();
+
+            if (n != goal.length()) {
+                return false;
+            }
+
+            String ss = s + s;
+
+            // try every possible starting position of ss
+            for (int i = 0; i < n; i++) {
+                if (ss.substring(i, i + n).equals(goal)) {
+                    return true;
+                }
+            }
+            return false;
+        }
+    }
 }

src/test/kotlin/com/github/dkoval/leetcode/challenge/RotateStringTest.kt

@@ -1,6 +1,7 @@
 package com.github.dkoval.leetcode.challenge
 
 import com.github.dkoval.leetcode.challenge.RotateString.RotateStringRev1
+import com.github.dkoval.leetcode.challenge.RotateString.RotateStringRev2
 import org.junit.jupiter.api.Assertions.assertEquals
 import org.junit.jupiter.api.Nested
 import org.junit.jupiter.api.extension.ExtensionContext
@@ -33,6 +34,20 @@ internal class RotateStringTest {
             RotateStringRev1().test(s, goal, expected)
         }
     }
+
+    @Nested
+    inner class RotateStringRev2Test {
+
+        @ParameterizedTest
+        @ArgumentsSource(InputArgumentsProvider::class)
+        fun `should return true if and only if s can become goal after some number of shifts on s`(
+            s: String,
+            goal: String,
+            expected: Boolean
+        ) {
+            RotateStringRev2().test(s, goal, expected)
+        }
+    }
 }
 
 private fun RotateString.test(s: String, goal: String, expected: Boolean) {