a.cpp

#include "Linked Stack.h"
#include <iostream>  // I/O definitions
using namespace std; // make std:: accessible
#include <vector>
#include <fstream>
#include <string>

vector<string> getHtmlTags()
{
    vector<string> tags; // vector of html tags

    ifstream fin("a.html");

    string line;
    while (getline(fin, line)) // read until end of file
    {
        int pos = 0;                  // current scan position
        int ts = line.find("<", pos); // possible tag start

        while (ts != string::npos) // repeat until end of string
        {
            int te = line.find(">", ts + 1);              // scan for tag end
            tags.push_back(line.substr(ts, te - ts + 1)); // append tag to the vector
            pos = te + 1;                                 // advance our position
            ts = line.find("<", pos);
        }
    }
    return tags; // return vector of tags

    bool isHtmlMatched(const vector<string> &tags)
    {
        LinkedStack S;                               // stack for opening tags
        typedef vector<string>::const_iterator Iter; // iterator type

        // iterate through vector
        for (Iter p = tags.begin(); p != tags.end(); ++p)

            if (p->at(1) != '/') // opening tag?
                S.push(*p);      // push it on the stack
            else
            { // else must be closing tag
                if (S.empty())
                    return false;                // nothing to match - failure
                string open = S.top().substr(1); // opening tag excluding ’<’
                string close = p->substr(2);     // closing tag excluding ’</’

                if (open.compare(close) != 0)
                    return false; // fail to match
                else
                    S.pop(); // pop matched element
            }
    }

    if (S.empty())
        return true; // everything matched - good
    else
        return false; // some unmatched - bad
}

int main()
{
    if (isHtmlMatched(getHtmlTags())) // get tags and test them
        cout << "The input file is a matched HTML document." << endl;
    else
        cout << "The input file is not a matched HTML document." << endl;

    ::getchar();
}