2016 Update

Task/Levenshtein-distance/JavaScript/levenshtein-distance-1.js

@@ -0,0 +1,31 @@
+function levenshtein(a, b) {
+  var t = [], u, i, j, m = a.length, n = b.length;
+  if (!m) { return n; }
+  if (!n) { return m; }
+  for (j = 0; j <= n; j++) { t[j] = j; }
+  for (i = 1; i <= m; i++) {
+    for (u = [i], j = 1; j <= n; j++) {
+      u[j] = a[i - 1] === b[j - 1] ? t[j - 1] : Math.min(t[j - 1], t[j], u[j - 1]) + 1;
+    } t = u;
+  } return u[n];
+}
+
+// tests
+[ ['', '', 0],
+  ['yo', '', 2],
+  ['', 'yo', 2],
+  ['yo', 'yo', 0],
+  ['tier', 'tor', 2],
+  ['saturday', 'sunday', 3],
+  ['mist', 'dist', 1],
+  ['tier', 'tor', 2],
+  ['kitten', 'sitting', 3],
+  ['stop', 'tops', 2],
+  ['rosettacode', 'raisethysword', 8],
+  ['mississippi', 'swiss miss', 8]
+].forEach(function(v) {
+  var a = v[0], b = v[1], t = v[2], d = levenshtein(a, b);
+  if (d !== t) {
+    console.log('levenstein("' + a + '","' + b + '") was ' + d + ' should be ' + t);
+  }
+});

Task/Levenshtein-distance/JavaScript/levenshtein-distance-2.js

@@ -0,0 +1,73 @@
+(() => {
+    'use strict';
+
+    // levenshtein :: String -> String -> Int
+    const levenshtein = (sa, sb) => {
+        const [s1, s2] = [sa.split(''), sb.split('')];
+
+        return last(s2.reduce((ns, c) => {
+            const [n, ns1] = uncons(ns);
+
+            return scanl(
+                (z, [c1, x, y]) =>
+                minimum(
+                    [y + 1, z + 1, x + fromEnum(c1 != c)]
+                ),
+                n + 1,
+                zip3(s1, ns, ns1)
+            );
+        }, range(0, s1.length)));
+    };
+
+
+    /*********************************************************************/
+    // GENERIC FUNCTIONS
+
+    // minimum :: [a] -> a
+    const minimum = xs =>
+        xs.reduce((a, x) => (x < a || a === undefined ? x : a), undefined);
+
+    // fromEnum :: Enum a => a -> Int
+    const fromEnum = x => {
+        const type = typeof x;
+        return type === 'boolean' ? (
+            x ? 1 : 0
+        ) : (type === 'string' ? x.charCodeAt(0) : undefined);
+    };
+
+    // uncons :: [a] -> Maybe (a, [a])
+    const uncons = xs => xs.length ? [xs[0], xs.slice(1)] : undefined;
+
+    // scanl :: (b -> a -> b) -> b -> [a] -> [b]
+    const scanl = (f, a, xs) => {
+        for (var lst = [a], lng = xs.length, i = 0; i < lng; i++) {
+            a = f(a, xs[i], i, xs), lst.push(a);
+        }
+        return lst;
+    };
+
+    // zip3 :: [a] -> [b] -> [c] -> [(a,b,c)]
+    const zip3 = (xs, ys, zs) =>
+        xs.slice(0, Math.min(xs.length, ys.length, zs.length))
+        .map((x, i) => [x, ys[i], zs[i]]);
+
+    // last :: [a] -> a
+    const last = xs => xs.length ? xs.slice(-1) : undefined;
+
+    // range :: Int -> Int -> [Int]
+    const range = (m, n) =>
+        Array.from({
+            length: Math.floor(n - m) + 1
+        }, (_, i) => m + i);
+
+    /*********************************************************************/
+    // TEST
+    return [
+        ["kitten", "sitting"],
+        ["sitting", "kitten"],
+        ["rosettacode", "raisethysword"],
+        ["raisethysword", "rosettacode"]
+    ].map(pair => levenshtein.apply(null, pair));
+
+    // -> [3, 3, 8, 8]
+})();

Task/Levenshtein-distance/JavaScript/levenshtein-distance-3.js

@@ -0,0 +1 @@
+[3, 3, 8, 8]

Task/Levenshtein-distance/JavaScript/levenshtein-distance.js

@@ -1,24 +0,0 @@
-function levenshtein(str1, str2) {
-    var m = str1.length,
-        n = str2.length,
-        d = [],
-        i, j;
-	
-    if (!m) return n;
-    if (!n) return m;
-	
-    for (i = 0; i <= m; i++) d[i] = [i];
-    for (j = 0; j <= n; j++) d[0][j] = j;
-	
-    for (j = 1; j <= n; j++) {
-        for (i = 1; i <= m; i++) {
-            if (str1[i-1] == str2[j-1]) d[i][j] = d[i - 1][j - 1];
-            else d[i][j] = Math.min(d[i-1][j], d[i][j-1], d[i-1][j-1]) + 1;
-        }
-    }
-    return d[m][n];
-}
-
-console.log(levenshtein("kitten", "sitting"));
-console.log(levenshtein("stop", "tops"));
-console.log(levenshtein("rosettacode", "raisethysword"));