/// <summary>
/// Reads a sequence of 8-bit bytes from standard input; compresses
/// them using LZW compression with 12-bit codewords; and writes the results
/// to standard output.</summary>
///
public void Compress()
{
string inputChars = input.ReadString();
TST <int> st = new TST <int>();
for (int i = 0; i < R; i++)
{
st.Put("" + (char)i, i);
}
int code = R + 1; // R is codeword for EOF
while (inputChars.Length > 0)
{
string s = st.LongestPrefixOf(inputChars); // Find max prefix match s.
output.Write(st[s], W); // Print s's encoding.
int t = s.Length;
if (t < inputChars.Length && code < L) // Add s to symbol table.
{
st.Put(inputChars.Substring(0, t + 1), code++);
}
inputChars = inputChars.Substring(t); // Scan past s in input.
}
output.Write(R, W);
output.Close();
}
/// <summary>
/// Reads a sequence of 8-bit bytes from standard input; compresses them
/// using Huffman codes with an 8-bit alphabet; and writes the results
/// to standard output.</summary>
///
public void Compress()
{
// read the input
string s = input.ReadString();
char[] inputChars = s.ToCharArray();
// tabulate frequency counts
int[] freq = new int[R];
for (int i = 0; i < inputChars.Length; i++)
{
freq[inputChars[i]]++;
}
// build Huffman trie
Node root = buildTrie(freq);
// build code table
string[] st = new string[R];
buildCode(st, root, "");
// print trie for decoder
writeTrie(root);
// print number of bytes in original uncompressed message
output.Write(inputChars.Length);
// use Huffman code to encode input
for (int i = 0; i < inputChars.Length; i++)
{
string code = st[inputChars[i]];
for (int j = 0; j < code.Length; j++)
{
if (code[j] == '0')
{
output.Write(false);
}
else if (code[j] == '1')
{
output.Write(true);
}
else
{
throw new InvalidOperationException("Illegal state");
}
}
}
// close output stream
output.Close();
}
/// <summary>
/// Reads a sequence of 8-bit extended ASCII characters over the alphabet
/// { A, C, T, G } from standard input; compresses them using two bits per
/// character; and writes the results to standard output.</summary>
///
public void Compress()
{
string s = input.ReadString();
int N = s.Length;
output.Write(N);
// Write two-bit code for char.
for (int i = 0; i < N; i++)
{
int d = DNA.ToIndex(s[i]);
output.Write(d, 2);
}
output.Close();
input.Close();
}
