assert(minLetter <= maxLetter);

const size_t nLetters = static_cast<int>(maxLetter) - static_cast<int>(minLetter) + 1;

std::uniform_int_distribution<size_t> distr(0, nLetters - 1);

std::mt19937 gen(seed);

string res;

res.reserve(n);

for (size_t i = 0; i < n; ++i)

res.push_back('a' + distr(gen));

return res;

const auto n = s.size();

const auto d_odd = manacher_odd(s);

if (d_odd.size() != n)

return false;

const auto inRange = [&](size_t idx) {

return idx >= 0 && idx < n;

};

for (size_t i = 0; i < n; ++i) {

if (d_odd[i] < 0)

return false;

for (int d = 0; d < d_odd[i]; ++d) {

const auto idx1 = i - d;

const auto idx2 = i + d;

if (!inRange(idx1) || !inRange(idx2))

return false;

if (s[idx1] != s[idx2])

return false;

}

const auto idx1 = i - d_odd[i];

const auto idx2 = i + d_odd[i];

if (inRange(idx1) && inRange(idx2) && s[idx1] == s[idx2])

return false;

}

return true;

vector<string> testCases;

testCases.push_back("");

for (size_t i = 1; i <= 25; ++i) {

auto s = string{};

s.resize(i, 'a');

testCases.push_back(move(s));

}

testCases.push_back("abba");

testCases.push_back("abccbaasd");

for (size_t n = 9; n <= 100; n += 10)

testCases.push_back(getRandomString(n, /* seed */ n, 'a', 'd'));

for (size_t n = 7; n <= 100; n += 10)

testCases.push_back(getRandomString(n, /* seed */ n));

for (const auto &s: testCases)

assert(testManacherOdd(s));

return 0;