gistfile1.cpp

#include <iostream>
#include <string>
using namespace std;

int subseq(std::string str, std::string pattern)
{
    size_t lastpos = 0;
    size_t occur = 0;

    if (!str.size() || !pattern.size()) {
        cout << "Sem ocorrencias" << endl;
        return 0;
    }

    while (1) {
        lastpos = str.find(pattern[0], lastpos);
        if (lastpos == string::npos)
            break;
        lastpos++;

        bool isok = true;
        for (size_t i = 1, lastsub = lastpos; i < pattern.size(); i++) {
            lastsub = str.find(pattern[i], lastpos);
            if (lastsub == string::npos) {
                isok = false;
            }
            lastsub++;
        }
        if (isok)
            ++occur;
    }
    cout << "Ocorrencias " << occur << endl;
    return occur;
}


int main()
{
    subseq("3141592653", "123");
    subseq("31415926531323", "123");
    return 0;
}