def expand():
"""
Reads a sequence of bit encoded using LZW compression with
12-bit codewords from standard input; expands them; and writes
the results to standard output.
"""
st = ["" for i in range(0, _L)]
i = 0
while (i < _R):
st[i] = "" + chr(i)
i += 1
st[i] = ""
i += 1
codeword = BinaryStdIn.read_int(_W)
if (codeword == _R):
return
val = st[codeword]
while (True):
BinaryStdOut.write_string(val)
codeword = BinaryStdIn.read_int(_W)
if (codeword == _R):
break
s = st[codeword]
if (i == codeword):
s = val + val[0]
if (i < _L):
st[i] = val + s[0]
i += 1
val = s
BinaryStdOut.close()
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 expand():
"""Reads a sequence of bits that represents a Huffman-compressed message from
standard input; expands them; and writes the results to standard output."""
BinaryStdIn.is_empty()
root = _read_trie()
length = BinaryStdIn.read_int()
for _ in range(0, length):
x = root
while not x.is_leaf():
bit = BinaryStdIn.read_bool()
if bit:
x = x.right
else:
x = x.left
BinaryStdOut.write_char(x.ch)
BinaryStdOut.close()
def _write_trie(x):
if x.is_leaf():
BinaryStdOut.write_bool(True)
BinaryStdOut.write_char(x.ch)
return
BinaryStdOut.write_bool(False)
_write_trie(x.left)
_write_trie(x.right)
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()
def main():
while (not BinaryStdIn.is_empty()):
BinaryStdOut.write_char(BinaryStdIn.read_char())