How do I read different types of text files (UNICODE or ASCII) in C++ and store its words in a hash table of std::string

ios::sync_with_stdio(false);
	locale loc;
	if(os=='W')
		loc.global(locale(""));
	else
		loc.global(locale("en_US.UTF-8"));
	wcout.imbue(loc);
	if(os=='W')
		system("dir /b *.txt > files.dat");
	else
		system("ls *.txt > files.dat");
	vector<string> FileList;
	string file;
	ifstream fp("files.dat");
	fp>>file;
	while(!fp.eof())
	{
		FileList.push_back(file);
		fp>>file;
	}
	fp.close();
	int NofFile=FileList.size();
	int choice, slot, i, j, c;
	pair<string,int> SortedFiles[NofFile];
	wstring str;
	string s;
	cout<<"\n\nChoose a method : \n";
	cout<<"1. Hash tables\n";
	cout<<"2. Tries\n";
	cout<<"3. Boyer Moore Algorithm\n";
	cout<<"Enter choice : ";
	cin>>choice;
	list<string> H[m][NofFile];
	list<string> B[NofFile];
	wifstream FP;
	switch(choice)
	{
		case 1:
			
			for(int f=0;f<NofFile;f++)
			{
				char* CurrFile=&FileList[f][0];
				FP.open(CurrFile);
				FP.imbue(loc);
				FP>>str;
				while(!FP.eof())
				{
					string s( str.begin(), str.end() );
					i=0;
					j=s.length();
					if(!s.empty())
					{
						while(!isalnum(s[i])) i++;
						while(!isalnum(s[j])) j--;
					}
					if(j>=i)
					{
						s=s.substr(i,j-i+1);
						transform(s.begin(), s.end(), s.begin(), ::tolower);
						slot=h(s);
						H[slot][f].push_front(s);
					}
					FP>>str;
				}
				FP.close();
			}
			cout<<"Enter a word to search : ";
			cin>>s;
			transform(s.begin(), s.end(), s.begin(), ::tolower);
			slot=h(s);
			for(int f=0;f<NofFile;f++)
			{
				SortedFiles[f].first=FileList[f];
				SortedFiles[f].second=count(H[slot][f].begin(),H[slot][f].end(),s);
			}
			break;