lzw演算法思想舉例：

原輸入資料為:A B A B A B A B B B A B A B A A C D A C D A D C A B A A A B A B .....
採用LZW演算法對其進行壓縮，壓縮過程用一個表來表述為:
注意原資料中只包含4個character,A,B,C,D
用兩bit即可表述，根據lzw演算法，首先擴充套件一位變為3為,Clear=2的2次方+1=4; End=4+1=5;
初始標號集因該為

演算法實現：

#include <string>
#include <map>
#include <iostream>
#include <iterator>
#include <vector>

// Compress a string to a list of output symbols.
// The result will be written to the output iterator
// starting at "result"; the final iterator is returned.
void compress(const std::string &uncompressed, std::vector<int>& vec) {
	// Build the dictionary.
	int dictSize = 256;
	std::map<std::string,int> dictionary;
	for (int i = 0; i < 256; i++)
	{
		dictionary[std::string(1, i)] = i;   
   	}
		
	std::string w;
	for (std::string::const_iterator it = uncompressed.begin();
		 it != uncompressed.end(); ++it) {
		char c = *it;
		std::string wc = w + c;
		if (dictionary.count(wc))
			w = wc;
		else {
			vec.push_back(dictionary[w]);
			// Add wc to the dictionary.
			dictionary[wc] = dictSize++;
			w = std::string(1, c);
		}
	}
 
	// Output the code for w.
	if (!w.empty())
		vec.push_back( dictionary[w]);
}
 
// Decompress a list of output ks to a string.
// "begin" and "end" must form a valid range of ints

std::string decompress(std::vector<int>& vec) {
	// Build the dictionary.
	int dictSize = 256;
	std::map<int,std::string> dictionary;
	for (int i = 0; i < 256; i++)
		dictionary[i] = std::string(1, i);

	std::vector<int>::iterator it = vec.begin();
	std::string w(1, *it);
	std::string result = w;
	std::string entry;
	for ( it++; it != vec.end(); it++) {
		int k = *it;
		if (dictionary.count(k))
			entry = dictionary[k];
		else if (k == dictSize)
			entry = w + w[0];
		else
			throw "Bad compressed k";
 
		result += entry;
 
		// Add w+entry[0] to the dictionary.
		dictionary[dictSize++] = w + entry[0];
 
		w = entry;
	}
	return result;
}
 
int main() {
	std::vector<int> compressed;
	compress("TOBEORNOTTOBEORTOBEORNOT", compressed);
	copy(compressed.begin(), compressed.end(), std::ostream_iterator<int>(std::cout, ", "));
	std::cout << std::endl;
	std::string decompressed = decompress(compressed);
	std::cout << decompressed << std::endl;

	return 0;
}
 

http://rosettacode.org/wiki/LZW_compression