Data update

Task/Burrows-Wheeler-transform/Sidef/burrows-wheeler-transform-2.sidef

@@ -0,0 +1,81 @@
+define LOOKAHEAD_LEN = 128
+
+func bwt_sort (String s) {    # O(n * LOOKAHEAD_LEN) space (fast)
+    ^s.len -> map {|i|
+        var t = s.slice(i, LOOKAHEAD_LEN)
+
+        if (t.len < LOOKAHEAD_LEN) {
+            t += s.slice(0, min(i, LOOKAHEAD_LEN - t.len))
+        }
+
+        [t, i]
+    }.sort {|a,b|
+        (a[0] <=> b[0]) || (s.rotate(a[1]) <=> s.rotate(b[1]))
+    }.map { .[1] }
+}
+
+func bwt_encode(String s) {
+
+    var bwt    = bwt_sort(s)
+    var ret    = bwt.map {|i| s.slice(i-1, 1) }.join
+    var prefix = s.slice(0, LOOKAHEAD_LEN)
+    var len    = prefix.len
+
+    var idx = 0;
+    for i in (bwt) {
+
+        var lookahead = s.slice(i, len)
+
+        if (lookahead.len < len) {
+            lookahead += s.slice(0, len - lookahead.len)
+        }
+
+        if (lookahead == prefix) {
+            var row = s.rotate(i)
+            if (row == s) {
+                break
+            }
+        }
+        ++idx
+    }
+
+    return (ret, idx)
+}
+
+func bwt_decode(String bwt, Number idx) {    # fast inversion
+
+    var tail = bwt.chars
+    var head = tail.sort
+
+    var indices = Hash()
+    tail.each_kv {|i,v|
+        indices{v} := [] << i
+    }
+
+    var table = []
+    head.each_kv {|i,v|
+        table[i] = indices{v}.shift
+    }
+
+    var dec = ''
+    var i = idx
+
+    head.len.times {
+        dec += head[i]
+        i = table[i]
+    }
+
+    return dec
+}
+
+var tests = [
+    "banana", "appellee", "dogwood", "TOBEORNOTTOBEORTOBEORNOT"
+    "SIX.MIXED.PIXIES.SIFT.SIXTY.PIXIE.DUST.BOXES",
+]
+
+tests.each { |str|
+    var (enc, idx) = bwt_encode(str)
+    var dec = bwt_decode(enc, idx)
+    say "BWT(#{dec.dump}) = (#{enc.dump}, #{idx})"
+    assert_eq(str, dec)
+}

Task/Burrows-Wheeler-transform/Wren/burrows-wheeler-transform.wren

@@ -1,4 +1,4 @@
-import "/sort" for Sort
+import "./sort" for Sort
 
 var stx = "\x02"
 var etx = "\x03"