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Refactor solution #2

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fa4f1ac
Use src/huffman.js in demo
Syeoryn Oct 22, 2015
3c022ca
Merge pull request #1 from Syeoryn/master
Oct 29, 2015
fb671e4
(Feat) Add solutions
Oct 20, 2015
603aeca
Fix code to pass specs
Syeoryn Oct 22, 2015
5e9ca1d
Move solution to src/huffman.js
Syeoryn Oct 22, 2015
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1 change: 0 additions & 1 deletion .gitignore
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Original file line number Diff line number Diff line change
@@ -1 +0,0 @@
solution
89 changes: 2 additions & 87 deletions Demo.html
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Expand Up @@ -4,6 +4,7 @@
<script src="lib/jquery.js"></script>
<script src="src/priorityQueue.js"></script>
<script src="src/misc.js"></script>
<script src="src/huffman.js"></script>
</head>
<body>
<div class='column c1'>
Expand Down Expand Up @@ -107,92 +108,6 @@ <h2>Efficiency:</h2>
}
</style>
<script>
var countChars = function(input) {
var counts = {};
for (var i = 0; i < input.length; i++) {
var c = input[i];
counts[c] = counts[c] || 0;
counts[c]++;
}
return counts;
};

var makeHuffmanTree = function(input) {
var charCounts = countChars(input);
var pq = new PriorityQueue();

for (var c in charCounts) {
var n = charCounts[c];
var tree = new Tree([c]);
pq.insert(n, tree);
}

while (pq.size() > 1) {
var first = pq.extract();
var second = pq.extract();

var tree1 = first.val;
var tree2 = second.val;

var key1 = first.key;
var key2 = second.key;

var newTree = new Tree(tree1.val.concat(tree2.val));
newTree.left = tree1;
newTree.right = tree2;
pq.insert(key1+key2, newTree);
}

return pq.extract().val;
};

var encodeChar = function(c, huffman) {
var output = "";
while (huffman.val.length > 1) {
if (huffman.left.val.indexOf(c) !== -1) {
huffman = huffman.left;
output += "0";
} else if (huffman.right.val.indexOf(c) !== -1) {
huffman = huffman.right;
output += "1";
} else {
throw new Error("Character " + c + " is not in this Huffman tree.");
}
}
return output;
};

var encodeString = function(input, huffman) {
var output = "";
for (var i = 0; i < input.length; i++) {
output += encodeChar(input[i], huffman);
}
return output;
};

var decodeString = function(input, huffman) {
var output = "";
var currNode = huffman;
for (var currIdx = 0; currIdx < input.length; currIdx++) {
var currBit = input[currIdx];
if (currBit === "0") {
currNode = currNode.left;
} else if (currBit === "1") {
currNode = currNode.right;
} else {
throw new Error("String to decode must consist of only 0s and 1s.");
}
if (currNode.val.length === 1) {
output += currNode.val[0];
currNode = huffman;
}
}
if (currNode !== huffman) {
throw new Error("String cannot be decoded - make sure you aren't missing any bits!");
}
return output;
};

var getDictionaryFromTree = function(tree) {
var result = {};

Expand Down Expand Up @@ -315,4 +230,4 @@ <h2>Efficiency:</h2>

</script>
</body>
</html>
</html>
75 changes: 75 additions & 0 deletions solution/solution.js
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@@ -0,0 +1,75 @@
var countChars = function(input) {
var counts = {};
for (var i = 0; i < input.length; i++) {
var c = input[i];
counts[c] = counts[c] || 0;
counts[c]++;
}
return counts;
};

var makeHuffmanTree = function(input) {
var charCounts = countChars(input);
var pq = new PriorityQueue();
for (var c in charCounts) {
var n = charCounts[c];
var tree = new Tree([c]);
pq.insert(n, tree);
}

while (pq.size() > 1) {
var first = pq.extract();
var second = pq.extract();

var tree1 = first.val;
var tree2 = second.val;

var key1 = first.key;
var key2 = second.key;

var newTree = new Tree(tree1.val.concat(tree2.val));
newTree.left = tree1;
newTree.right = tree2;
pq.insert(key1+key2, newTree);
}

return pq.extract().val;
};

var encodeString = function(input, huffman) {
var output = "";
for (var i = 0; i < input.length; i++) {
var currentNode = huffman;
var nextCharacter = input[i];
while (currentNode.val.length > 1) {
if (currentNode.left.val.indexOf(nextCharacter) !== -1) {
currentNode = currentNode.left;
output += "0";
} else if (currentNode.right.val.indexOf(nextCharacter) !== -1) {
currentNode = currentNode.right;
output += "1";
} else {
throw new Error("Character " + nextCharacter + " is not in this Huffman tree.");
}
}
}
return output;
};

var decodeString = function(input, huffman) {
var output = "";
var currNode = huffman;
for (var currIdx = 0; currIdx < input.length; currIdx++) {
var currBit = input[currIdx];
if (currBit === "0") {
currNode = currNode.left;
} else if (currBit === "1") {
currNode = currNode.right;
}
if (currNode.val.length === 1) {
output += currNode.val[0];
currNode = huffman;
}
}
return output;
};
81 changes: 72 additions & 9 deletions src/huffman.js
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@@ -1,13 +1,43 @@
// // Given a Huffman tree and a string, encode that string into a new string
// // consisting only of 1s and 0s, using the code given by the tree.
var encodeString = function(input, huffmanTree) {
return "";
// Given a Huffman tree and a string, encode that string into a new string
// consisting only of 1s and 0s, using the code given by the tree.
var encodeString = function(input, huffman) {
var output = "";
for (var i = 0; i < input.length; i++) {
var currentNode = huffman;
var nextCharacter = input[i];
while (currentNode.val.length > 1) {
if (currentNode.left.val.indexOf(nextCharacter) !== -1) {
currentNode = currentNode.left;
output += "0";
} else if (currentNode.right.val.indexOf(nextCharacter) !== -1) {
currentNode = currentNode.right;
output += "1";
} else {
throw new Error("Character " + nextCharacter + " is not in this Huffman tree.");
}
}
}
return output;
};

// // Given a Huffman tree and a string of 1s and 0s, decode that string into
// // a new, human-readable string, using the code given by the tree.
var decodeString = function(input, huffmanTree) {
return "";
// Given a Huffman tree and a string of 1s and 0s, decode that string into
// a new, human-readable string, using the code given by the tree.
var decodeString = function(input, huffman) {
var output = "";
var currNode = huffman;
for (var currIdx = 0; currIdx < input.length; currIdx++) {
var currBit = input[currIdx];
if (currBit === "0") {
currNode = currNode.left;
} else if (currBit === "1") {
currNode = currNode.right;
}
if (currNode.val.length === 1) {
output += currNode.val[0];
currNode = huffman;
}
}
return output;
};

// Given a corpus of text, return a Huffman tree that represents the
Expand All @@ -22,6 +52,39 @@ var decodeString = function(input, huffmanTree) {
// You may also use the `Tree` class that is provided in the file `misc.js`
// Some corpuses are included as the variables `lorumIpsum` and `declaration`.
var makeHuffmanTree = function(corpus) {
return new Tree();
var charCounts = countChars(corpus);
var pq = new PriorityQueue();
for (var c in charCounts) {
var n = charCounts[c];
var tree = new Tree([c]);
pq.insert(n, tree);
}

while (pq.size() > 1) {
var first = pq.extract();
var second = pq.extract();

var tree1 = first.val;
var tree2 = second.val;

var key1 = first.key;
var key2 = second.key;

var newTree = new Tree(tree1.val.concat(tree2.val));
newTree.left = tree1;
newTree.right = tree2;
pq.insert(key1+key2, newTree);
}

return pq.extract().val;
};

var countChars = function(input) {
var counts = {};
for (var i = 0; i < input.length; i++) {
var c = input[i];
counts[c] = counts[c] || 0;
counts[c]++;
}
return counts;
};