lachlan · September 28, 2012 00:35 · Sep 28, 2012
diff --git a/anagrams.js b/anagrams.js
@@ -0,0 +1,56 @@
+var fs = require('fs'),
+    filename = 'words.txt',
+    encoding = 'utf-8';
+
+fs.readFile(filename, encoding, function(err, data) {
+  if (err) throw err;
+
+  var lines = data.split('\n');
+
+  // trim whitespace, and convert to lower case
+  for (var i = 0; i < lines.length; i++) {
+    lines[i] = lines[i].trim().toLowerCase();
+  }
+
+  // remove all duplicate lines
+  lines = lines.filter(function(item, index, array) {
+    return index == array.indexOf(item);
+  });
+
+  // for each word sort the characters alphabetically to create
+  // a hash key (all anagrams will generate the same key!)
+  // and then append this word to the list of all other words
+  // with the same key
+  var words = {};
+
+  for (var i = 0; i < lines.length; i++) {
+    var word = lines[i];
+    if (word !== '') {
+      // generate an anagram key by sorting all characters alphabetically
+      var key = word.split('').sort().join('');
+      // get the list of anagrams that match this word from the hash table
+      var list = words[key] || [];
+      // add this word to the other anagrams with this key
+      list.push(word);
+      // assign the list back to the anagram hash table
+      words[key] = list;
+    }
+  }
+
+  // create a list of anagrams from the hash table, exclude words with no anagrams
+  var anagrams = [];
+  for (var key in words) {
+    if (words.hasOwnProperty(key)) {
+      if (words[key].length > 1) anagrams.push(words[key]);
+    }
+  }
+
+  // sort the list by the number of anagrams descending
+  anagrams.sort(function(a, b) {
+    return (b.length - a.length);
+  });
+
+  // print results
+  console.log("# anagrams found: " + anagrams.length);
+  console.log(anagrams.join("\n"));
+});