Longest common substring constrained by pattern
#include <iostream>

const std::string longestCommonSubstring(int, std::string const& s1, std::string const& s2, std::string const& s3);

int main(void) {
    std::string s1="hello 5", s2="bolo 7", s3="lo 9sdf";
    std::cout << "Trying to get "lo 5", actual result: "" << longestCommonSubstring(5, s1, s2, s3) << '"';
}

const std::string longestCommonSubstring(int must_include, std::string const& s1, std::string const& s2, std::string const& s3) {
    std::string longest;

    for(size_t start=0, length=1; start + length <= s1.size();) {
        std::string tmp = s1.substr(start, length);
        if (std::string::npos != s2.find(tmp) && std::string::npos != s3.find(tmp)) {
            tmp.swap(longest);
            ++length;
        } else ++start;
    }

    return longest;
}

//find all pattern sequences
N1 = findAllPatterns(s1, number);
 for i = 2 to n:
  for item in Ni-1:
   for match in findAllPatterns(si, nextPattern(item))
    Ni.add([item, (match, indexOf(match))]);

//for all pattern sequences identify the max common substring
maxCommonLength = 0;
for sequence in Nn:
 temp = findLCS(sequence);
 if(length(temp[0]) > maxCommonLength):
  maxCommonLength = length(temp[0]);
  result = temp;

return result;

#include <iostream>
#include <string>
#include <sstream>
#include <vector>

typedef std::pair<std::pair<std::string, std::string>, std::pair<std::pair<std::string, std::string>, std::pair<std::string, std::string>>> pairStringTrio;
typedef std::pair<std::string,std::pair<std::string,std::string>> stringPairString;

stringPairString longestCommonSubstring(const pairStringTrio&);
std::string strFindReplace(const std::string&, const std::string&, const std::string&);

int main(void) {
        std::string s1= "6 HUMAN ACTIONb", s2="8 HUMAN ACTIONd", s3="10 HUMAN ACTIONf";
        pairStringTrio result = std::make_pair(std::make_pair(s1, "6"), std::make_pair(std::make_pair(s2, "8"), std::make_pair(s3, "10")));

        stringPairString answer = longestCommonSubstring(result);
        std::cout << '"' << answer.first << ""t"" << answer.second.first << ""t"" << answer.second.second << '"';
}


stringPairString longestCommonSubstring(const pairStringTrio &foo) {
        std::string longest;

        for(size_t start=0, length=foo.first.first.size()-1; start + length <= foo.first.first.size();) {
                std::string s1_tmp = foo.first.first.substr(start, length);
                std::string s2_tmp = strFindReplace(s1_tmp, foo.first.second, foo.second.first.second);
                std::string s3_tmp = strFindReplace(s1_tmp, foo.first.second, foo.second.second.second);

                if (std::string::npos != foo.second.first.first.find(s2_tmp) && std::string::npos != foo.second.second.first.find(s3_tmp)) {
                        s1_tmp.swap(longest);
                        ++length;
                } else ++start;
        }

        return std::make_pair(longest, std::make_pair(strFindReplace(longest, foo.first.second, foo.second.first.second), strFindReplace(longest, foo.first.second, foo.second.second.second)));
}

std::string strFindReplace(const std::string &original, const std::string& src, const std::string& dest) {
        std::string answer=original;
        for(std::size_t pos = 0; (pos = answer.find(src, pos)) != answer.npos;)
                answer.replace(pos, src.size(), dest);
        return answer;
}