def compress():
"""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
input."""
s = BinaryStdIn.read_string()
# Tabulate frequency counts
freq = [0 for i in range(0, _R)]
for i in range(0, len(s)):
freq[ord(s[i])] += 1
# Build Huffman trie
root = _build_trie(freq)
# Build code table
st = [None for i in range(0, _R)]
_build_code(st, root, "")
# Print trie for decoder
_write_trie(root)
# Print number of bytes in original uncompressed message
BinaryStdOut.write_int(len(s))
# Use Huffman code to encode input
for i in range(0, len(s)):
code = st[ord(s[i])]
for j in range(0, len(code)):
if code[j] == "0":
BinaryStdOut.write_bool(False)
elif code[j] == "1":
BinaryStdOut.write_bool(True)
else:
raise ValueError("Illegal state")
BinaryStdOut.close()
def compress():
"""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."""
input_ = BinaryStdIn.read_string()
st = TST()
for i in range(0, _R):
st.put("" + chr(i), i)
code = _R + 1
while len(input_) > 0:
s = st.longest_prefix_of(input_)
BinaryStdOut.write_int(st.get(s), _W)
t = len(s)
if t < len(input_) and code < _L:
st.put(input_[0 : t + 1], code)
code += 1
input_ = input_[t:]
BinaryStdOut.write_int(_R, _W)
BinaryStdOut.close()