How to find Longest Common Substring using C++

Question

I searched online for a C++ Longest Common Substring implementation but failed to find a decent one. I need a LCS algorithm that returns the substring itself, so it\'s not j

Answer 1

I tried several different solutions for this but they all seemed really slow so I came up with the below, didn't really test much, but it seems to work a bit faster for me.

#include 

std::string lcs( std::string a, std::string b )
{
    if( a.empty() || b.empty() ) return {} ;

    std::string current_lcs = "";

    for(int i=0; i< a.length(); i++) {
        size_t fpos = b.find(a[i], 0);
        while(fpos != std::string::npos) {
            std::string tmp_lcs = "";
            tmp_lcs += a[i];
            for (int x = fpos+1; x < b.length(); x++) {
                tmp_lcs+=b[x];
                size_t spos = a.find(tmp_lcs, 0);
                if (spos == std::string::npos) {
                    break;
                } else {
                    if (tmp_lcs.length() > current_lcs.length()) {
                        current_lcs = tmp_lcs;
                    }
                }
            }
            fpos = b.find(a[i], fpos+1);
        }
    }
    return current_lcs;
}

int main(int argc, char** argv)
{
    std::cout << lcs(std::string(argv[1]), std::string(argv[2])) << std::endl;
}