Initial data commit

Task/Burrows-Wheeler-transform/Java/burrows-wheeler-transform.java

@@ -0,0 +1,77 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class BWT {
+    private static final String STX = "\u0002";
+    private static final String ETX = "\u0003";
+
+    private static String bwt(String s) {
+        if (s.contains(STX) || s.contains(ETX)) {
+            throw new IllegalArgumentException("String cannot contain STX or ETX");
+        }
+
+        String ss = STX + s + ETX;
+        List<String> table = new ArrayList<>();
+        for (int i = 0; i < ss.length(); i++) {
+            String before = ss.substring(i);
+            String after = ss.substring(0, i);
+            table.add(before + after);
+        }
+        table.sort(String::compareTo);
+
+        StringBuilder sb = new StringBuilder();
+        for (String str : table) {
+            sb.append(str.charAt(str.length() - 1));
+        }
+        return sb.toString();
+    }
+
+    private static String ibwt(String r) {
+        int len = r.length();
+        List<String> table = new ArrayList<>();
+        for (int i = 0; i < len; ++i) {
+            table.add("");
+        }
+        for (int j = 0; j < len; ++j) {
+            for (int i = 0; i < len; ++i) {
+                table.set(i, r.charAt(i) + table.get(i));
+            }
+            table.sort(String::compareTo);
+        }
+        for (String row : table) {
+            if (row.endsWith(ETX)) {
+                return row.substring(1, len - 1);
+            }
+        }
+        return "";
+    }
+
+    private static String makePrintable(String s) {
+        // substitute ^ for STX and | for ETX to print results
+        return s.replace(STX, "^").replace(ETX, "|");
+    }
+
+    public static void main(String[] args) {
+        List<String> tests = List.of(
+            "banana",
+            "appellee",
+            "dogwood",
+            "TO BE OR NOT TO BE OR WANT TO BE OR NOT?",
+            "SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES",
+            "\u0002ABC\u0003"
+        );
+        for (String test : tests) {
+            System.out.println(makePrintable(test));
+            System.out.print(" --> ");
+            String t = "";
+            try {
+                t = bwt(test);
+                System.out.println(makePrintable(t));
+            } catch (IllegalArgumentException e) {
+                System.out.println("ERROR: " + e.getMessage());
+            }
+            String r = ibwt(t);
+            System.out.printf(" --> %s\n\n", r);
+        }
+    }
+}