Tests for finding minimal string rotation

Author: SzymonStankiewicz

test/com/jwetherell/algorithms/strings/test/StringRotation.java

@@ -0,0 +1,80 @@
+package com.jwetherell.algorithms.strings.test;
+
+import com.jwetherell.algorithms.strings.Rotation;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class StringRotation {
+
+    private String reverse(String text) {
+        return new StringBuilder(text).reverse().toString();
+    }
+
+    @Test
+    public void minimalRotationTest() {
+        assertEquals("",
+                Rotation.getLexicographicallyMinimalRotation(""));
+
+        assertEquals("a",
+                Rotation.getLexicographicallyMinimalRotation("a"));
+
+        assertEquals("abcdefgh",
+                Rotation.getLexicographicallyMinimalRotation("abcdefgh"));
+
+        assertEquals("abcdefgh",
+                Rotation.getLexicographicallyMinimalRotation("bcdefgha"));
+
+        assertEquals("abbbbbbb",
+                Rotation.getLexicographicallyMinimalRotation("bbbbbabb"));
+
+
+        StringBuilder builder = new StringBuilder();
+        for(char c = 'Z'; c > 'A'; c--) {
+            for(int i = 0; i<4000; i++)
+                builder.append(c);
+            for(char c2 = c; c2 <= 'Z'; c2++)
+                builder.append(c2);
+        }
+        String str = builder.toString();
+
+        assertEquals('A'+str+str,
+                Rotation.getLexicographicallyMinimalRotation(str + 'A' + str));
+
+        assertEquals('A'+str+reverse(str)+str,
+                Rotation.getLexicographicallyMinimalRotation(reverse(str) + str + 'A' + str));
+    }
+
+    @Test
+    public void maximalRotationTest() {
+        assertEquals("",
+                Rotation.getLexicographicallyMaximalRotation(""));
+
+        assertEquals("a",
+                Rotation.getLexicographicallyMaximalRotation("a"));
+
+        assertEquals("habcdefg",
+                Rotation.getLexicographicallyMaximalRotation("abcdefgh"));
+
+        assertEquals("habcdefg",
+                Rotation.getLexicographicallyMaximalRotation("habcdefg"));
+
+        assertEquals("cbbbbbbb",
+                Rotation.getLexicographicallyMaximalRotation("bbbbbcbb"));
+
+        StringBuilder builder = new StringBuilder();
+        for(char c = 'A'; c < 'Z'; c++) {
+            for(int i = 0; i<4000; i++)
+                builder.append(c);
+            for(char c2 = c; c2 >='A'; c2--)
+                builder.append(c2);
+        }
+        String str = builder.toString();
+
+        assertEquals('Z'+str+str,
+                Rotation.getLexicographicallyMaximalRotation(str + 'Z' + str));
+
+        assertEquals('Z'+str+reverse(str)+str,
+                Rotation.getLexicographicallyMaximalRotation(reverse(str) + str + 'Z' + str));
+    }
+}