Вычисление кол-ва предложений в строке

 for(i=0;i<(length(st)-2);i++)
if(st[i] == "." && st[i+1] == " ") 
count++;

#include <iostream>
#include <string>
 
std::string Delete_Blanks_and_Points (std::string Str)
{
        std::string S = Str;
        while (S.find("  ") < S.length())
                S.erase(S.find("  "), 1);
        while (S.find("..") < S.length())
                S.erase(S.find(".."), 1);
        return S;
}
 
int Number_Sentence (std::string Str)
{
    std::string Double_String = Delete_Blanks_and_Points (Str) + ".";
    int count_sentence = 0;
    while (!Double_String.empty())
    {
        if ((Double_String.find(".") <= Double_String.length()) ||
            (Double_String.find(". ") <= Double_String.length()))
            count_sentence++;
        Double_String.erase(0, Double_String.find(".") + 1);
    }
    return count_sentence;
}
 
int main()
{
    std::string main_string = "Qwerty...Qwerty... Qwerty!";
    std::cout << Delete_Blanks_and_Points (main_string) << std::endl;
    std::cout << Number_Sentence(main_string) << std::endl;
    std::cin.get();
    return 0;
}