Data update

Task/Burrows-Wheeler-transform/JavaScript/burrows-wheeler-transform.js

@@ -0,0 +1,76 @@
+class BWT {
+    static STX = "\u0002";
+    static ETX = "\u0003";
+
+    static bwt(s) {
+        if (s.includes(BWT.STX) || s.includes(BWT.ETX)) {
+            throw new Error("String cannot contain STX or ETX");
+        }
+
+        const ss = BWT.STX + s + BWT.ETX;
+        const table = [];
+        for (let i = 0; i < ss.length; i++) {
+            const before = ss.substring(i);
+            const after = ss.substring(0, i);
+            table.push(before + after);
+        }
+        table.sort();
+
+        let sb = "";
+        for (const str of table) {
+            sb += str.charAt(str.length - 1);
+        }
+        return sb;
+    }
+
+    static ibwt(r) {
+        const len = r.length;
+        const table = [];
+        for (let i = 0; i < len; ++i) {
+            table.push("");
+        }
+        for (let j = 0; j < len; ++j) {
+            for (let i = 0; i < len; ++i) {
+                table[i] = r.charAt(i) + table[i];
+            }
+            table.sort();
+        }
+        for (const row of table) {
+            if (row.endsWith(BWT.ETX)) {
+                return row.substring(1, len - 1);
+            }
+        }
+        return "";
+    }
+
+    static makePrintable(s) {
+        // substitute ^ for STX and | for ETX to print results
+        return s.replace(BWT.STX, "^").replace(BWT.ETX, "|");
+    }
+
+    static main() {
+        const tests = [
+            "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 (const test of tests) {
+            console.log(BWT.makePrintable(test));
+            process.stdout.write(" --> ");
+            let t = "";
+            try {
+                t = BWT.bwt(test);
+                console.log(BWT.makePrintable(t));
+            } catch (e) {
+                console.log("ERROR: " + e.message);
+            }
+            const r = BWT.ibwt(t);
+            console.log(` --> ${r}\n`);
+        }
+    }
+}
+
+BWT.main();