aadscomp

// datacomp.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <vector>
#include <string>
using namespace std;

const int dictsize = 9;
string dictionary = "AAAAAAAA";
string text = "ABABCDABCABCDCADABCA";
string textcpy = text;
string lookahead;
vector <string> subsets;
vector <string> compressed;

void substrings(string str) {
    subsets.erase(subsets.begin(), subsets.end());
    if (str.length() > 1) {
        for (int i = 0; i <= str.length(); i++) {
            string s1 = str.substr(0, i); //get a substring of s from from the start to index i
            subsets.push_back(s1);
        }
    }
    else {
        subsets.push_back(str);
    }
    if (subsets.size() > 1) {
        for (int i = 1;i < subsets.size();i++) {
            subsets[i - 1] = subsets[i]; //since there's an empty space at the start shift all values left
        }
    }
    subsets.erase(subsets.begin() + 4);//delete last entry because now it is empty
}

void compress() {
    if (textcpy.length() >= 4) {
        lookahead = textcpy.substr(0, 4);
    }
    else {
        lookahead = textcpy.substr(0, textcpy.length());
    }
    substrings(lookahead);
    string output = "(";
    int maxlen = 0;
    int maxidx = -1;
    for (int i = 0; i < subsets.size(); i++) {
        size_t index = dictionary.rfind(subsets[i]); //store index of found substring
                                                     //cout << "loop" << endl;
        if (dictionary.rfind(subsets[i]) != string::npos) { //if there is a match do this
                                                            //cout << "ifentered" << endl;
            if (subsets[i].length()>maxlen) { //execute if substring is the longest so far
                maxlen = subsets[i].length();
                maxidx = index;
            }
            //cout << "index of found: " << 7 - index << " length of found: " << subsets[i].length() << endl;

        }
    }

    if (maxlen > 0) {//if match is found
        cout << "dict: " << dictionary << endl;
        //cout << "text: " << textcpy << endl;
        cout << "lookahead: " << lookahead << endl;
        maxidx = 7 - maxidx;//reverse index since indexing in example is right to left
        output += "0,";
        output += to_string(maxidx);
        output += ",";
        output += to_string(maxlen);
        output += ")";
        cout << output << endl;
        compressed.push_back(output);

        for (int i = 1;i <= maxlen;i++) {//shift the dictionary to the left by the length amount
            for (int i = 1;i < dictionary.length();i++) {
                dictionary[i - 1] = dictionary[i]; //since there's an empty space at the start shift all values left
            }

        }
        dictionary.erase(8 - maxlen, maxlen);//remove as many ending characters as length of match
        dictionary.append(lookahead, 0, maxlen);
        textcpy.erase(0, maxlen);

    }
    else {
        cout << "dict: " << dictionary << endl;
        //cout << "text: " << textcpy << endl;
        cout << "lookahead: " << lookahead << endl;
        output += "1,";
        output += subsets[0];
        output += ")";
        cout << output << endl; //if no match then cout new char
        compressed.push_back(output);

        for (int i = 1;i < dictionary.length();i++) {
            dictionary[i - 1] = dictionary[i]; //since there's an empty space at the start shift all values left
        }
        dictionary.erase(7);//remove last character
        dictionary.append(lookahead, 0, 1); //add the new char
        textcpy.erase(0, 1);
    }
}


int main(void)
{

    cout << "dict: " << dictionary << endl;
    cout << "text: " << textcpy << endl;
    cout << "lookahead: " << lookahead << endl;
    while (textcpy.length() >= 4) {
        compress();
    }

    system("pause");
    return 0;

}