#include <iostream>
#include <string>
#include <regex>
#include <fstream>

std::string IntToString(int a) {
   std::string result;
   int number = abs(a);
   while (number) {
      result += (number % 10) + 48;
      number /= 10;
   }
   if (a < 0) result += '-';
   std::reverse(result.begin(), result.end());
   return result;
}

/////////////////////////////ЛЕКСИЧЕСКИЙ АНАЛИЗ////////////////////////////////
//список лексем
struct node {
    std::string id;
    int n;
    node *next;
};

node *head;
node *tail;

void addToList (std::string value, int i) {
    if (head == NULL) {
            head = new node();
            head->n = i;
            head->id = value;
            head->next = NULL;
            tail = head;
        }
        else {
            tail->next = new node();
            tail = tail->next;
            tail->n = i;
            tail->id = value;
            tail->next = NULL;
        }
}

int searchInList (std::string value) {
    //bool b;
    node *point = head;
    while (point != NULL) {
        if (value == point->id) {
            return point->n;
        }
        point = point->next;
    };
    return 0;
}

void removeList () {
    node *point = head;
    node *pBuf;
    while (point != NULL) {
        pBuf = point->next;
        delete point;
        point = pBuf;
    }
}

void searchLexemes(std::string& input, int& i, int type, std::ofstream& fout)
{
    std::string strBuf;
    switch (type) {
        case 1: { //переменные
            strBuf = "[a-z][a-z0-9]*";
            break;
        }
        case 2: { //числа с плавающей точкой
            strBuf = "\\d(\\.?\\d+)?E[+-]\\d+";
            break;
        }
        case 3: { //числа с фиксированной точкой
            strBuf = "[0-9]+\\.[0-9]+";
            break;
        }
        case 4: { //целые числа
            strBuf = "[0-9]+";
            break;
        }
    }

    std::cout << "Start search" << std::endl;

    std::smatch m;
    std::regex rExp(strBuf);
    strBuf = input;
    input = "";
    bool foundAny = false;
    int i2;
    while (std::regex_search (strBuf, m, rExp)) {
        auto x = m.str();
        std::cout << "Found " << x << std::endl;
        i2 = searchInList(x);
        std::cout << "i2 = " << i2 << std::endl;
        if (i2 == 0) { //новая лексема
            i2 = i;
            addToList(x, i);
            i++;
        }
        input += m.prefix();
        input += "i" + IntToString(i2);
        strBuf = m.suffix();
        foundAny = true;
        }
    foundAny ? input += m.suffix() : input = strBuf;
}

void main() {
    std::string input;
    input = "fgs1=(b+a*5.01E+10)+a*10+(c*10.5)*51E-10";

    std::ofstream fout;
    fout.open("OUTPUT.TXT");

    int intBuf;
    int i = 1; //номер последней лексеммы

    std::cout << input << std::endl;

    searchLexemes(input, i, 1, fout);
    searchLexemes(input, i, 2, fout);
    searchLexemes(input, i, 3, fout);
    searchLexemes(input, i, 4, fout);

    std::cout << input << std::endl;
    //ожидаемый результат - "i1=(i2+i3*i5)+i3*i8+(i4*i7)*i6"

    removeList();
    system ("pause");
}