Two ways to solve the "Longest common subsequence" problem

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    namespace v1    {        template <typename CHAR>        std::basic_string<CHAR> lcs(const CHAR * s1, const CHAR * s2)        {            typedef std::basic_string<CHAR> String;            String ret;            int m = s1 != NULL ? static_cast<int>(strlen(s1)) : 0;            int n = s2 != NULL ? static_cast<int>(strlen(s2)) : 0;            if (m > 0 && n > 0) {                std::vector<std::vector<String>> cache(m + 1, std::vector<String>(n + 1));                for (int i = m - 1; i >= 0; --i) {                    for (int j = n - 1; j >= 0; --j) {                        String r1 = cache[i + 1][j];                        String r2 = cache[i][j + 1];                        String r3;                        String * pr = r1.length() >= r2.length() ? &r1 : &r2;                        if (s1[i] == s2[j]) {                            r3.push_back(s1[i]);                            r3 += cache[i + 1][j + 1];                            if (pr->length() < r3.length()) {                                pr = &r3;                            }                        }                        cache[i][j] = std::move(*pr);                    }                }                ret.swap(cache[0][0]);            }            return std::move(ret);        }    }

    namespace v2    {        namespace details        {            struct record            {                int   length;                short row_increment;                short column_increment;            };            template <typename CHAR>            std::basic_string<CHAR> get_string(const CHAR * s1, const CHAR * s2, std::vector<std::vector<record>> const & cache)            {                std::basic_string<CHAR> ret;                for (int i = 0, j = 0; ; ) {                    const record & r = cache[i][j];                    if (r.row_increment != 0 || r.column_increment != 0) {                        if (r.row_increment == 1 && r.column_increment == 1) {                            ret.push_back(s1[i]);                        }                        i += r.row_increment;                        j += r.column_increment;                    }                    else {                        break;                    }                }                return std::move(ret);            }        }        template <typename CHAR>        std::basic_string<CHAR> lcs(const CHAR * s1, const CHAR * s2)        {            typedef std::basic_string<CHAR> String;            String ret;            int m = s1 != NULL ? static_cast<int>(strlen(s1)) : 0;            int n = s2 != NULL ? static_cast<int>(strlen(s2)) : 0;            if (m > 0 && n > 0) {                std::vector<std::vector<details::record>> cache(m + 1, std::vector<details::record>(n + 1, details::record{0, 0, 0}));                for (int i = m - 1; i >= 0; --i) {                    for (int j = n - 1; j >= 0; --j) {                        details::record r1 = { cache[i + 1][j].length, 1, 0 };                        details::record r2 = { cache[i][j + 1].length, 0, 1 };                        details::record r3 = { cache[i + 1][j + 1].length + 1, 1, 1 };                        details::record * pr = r1.length >= r2.length ? &r1 : &r2;                        if (s1[i] == s2[j]) {                            if (pr->length < r3.length) {                                pr = &r3;                            }                        }                        cache[i][j] = *pr;                    }                }                ret.swap(details::get_string(s1, s2, cache));            }            return std::move(ret);        }    }

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