Initial data commit

Task/Huffman-coding/JavaScript/huffman-coding-1.js

@@ -0,0 +1,63 @@
+function HuffmanEncoding(str) {
+    this.str = str;
+
+    var count_chars = {};
+    for (var i = 0; i < str.length; i++)
+        if (str[i] in count_chars)
+            count_chars[str[i]] ++;
+        else
+            count_chars[str[i]] = 1;
+
+    var pq = new BinaryHeap(function(x){return x[0];});
+    for (var ch in count_chars)
+        pq.push([count_chars[ch], ch]);
+
+    while (pq.size() > 1) {
+        var pair1 = pq.pop();
+        var pair2 = pq.pop();
+        pq.push([pair1[0]+pair2[0], [pair1[1], pair2[1]]]);
+    }
+
+    var tree = pq.pop();
+    this.encoding = {};
+    this._generate_encoding(tree[1], "");
+
+    this.encoded_string = ""
+    for (var i = 0; i < this.str.length; i++) {
+        this.encoded_string += this.encoding[str[i]];
+    }
+}
+
+HuffmanEncoding.prototype._generate_encoding = function(ary, prefix) {
+    if (ary instanceof Array) {
+        this._generate_encoding(ary[0], prefix + "0");
+        this._generate_encoding(ary[1], prefix + "1");
+    }
+    else {
+        this.encoding[ary] = prefix;
+    }
+}
+
+HuffmanEncoding.prototype.inspect_encoding = function() {
+    for (var ch in this.encoding) {
+        print("'" + ch + "': " + this.encoding[ch])
+    }
+}
+
+HuffmanEncoding.prototype.decode = function(encoded) {
+    var rev_enc = {};
+    for (var ch in this.encoding)
+        rev_enc[this.encoding[ch]] = ch;
+
+    var decoded = "";
+    var pos = 0;
+    while (pos < encoded.length) {
+        var key = ""
+        while (!(key in rev_enc)) {
+            key += encoded[pos];
+            pos++;
+        }
+        decoded += rev_enc[key];
+    }
+    return decoded;
+}