Another update from ingydotnet^djgoku

Task/Find-the-missing-permutation/JavaScript/find-the-missing-permutation-2.js

@@ -0,0 +1,40 @@
+(function (strList) {
+
+    // [a] -> [[a]]
+    function permutations(xs) {
+        return xs.length ? (
+            chain(xs, function (x) {
+                return chain(permutations(deleted(x, xs)), function (ys) {
+                    return [[x].concat(ys).join('')];
+                })
+            })) : [[]];
+    }
+
+    // Monadic bind/chain for lists
+    // [a] -> (a -> b) -> [b]
+    function chain(xs, f) {
+        return [].concat.apply([], xs.map(f));
+    }
+
+    // a -> [a] -> [a]
+    function deleted(x, xs) {
+        return xs.length ? (
+            x === xs[0] ? xs.slice(1) : [xs[0]].concat(
+                deleted(x, xs.slice(1))
+            )
+        ) : [];
+    }
+
+    // Provided subset
+    var lstSubSet = strList.split('\n');
+
+    // Any missing permutations
+    // (we can use fold/reduce, filter, or chain (concat map) here)
+    return chain(permutations('ABCD'.split('')), function (x) {
+        return lstSubSet.indexOf(x) === -1 ? [x] : [];
+    });
+
+})(
+    'ABCD\nCABD\nACDB\nDACB\nBCDA\nACBD\nADCB\nCDAB\nDABC\nBCAD\nCADB\n\
+CDBA\nCBAD\nABDC\nADBC\nBDCA\nDCBA\nBACD\nBADC\nBDAC\nCBDA\nDBCA\nDCAB'
+);

Task/Find-the-missing-permutation/JavaScript/find-the-missing-permutation-3.js

@@ -0,0 +1 @@
+["DBAC"]