Codeforces-solutions/Codeforces Round 937 (Div. 4)/E. Nearly Shortest Repeating Substring.cpp

185 lines
3.7 KiB
C++

/* Problem URL: https://codeforces.com/problemset/problem/1950/E */
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template <class T, class comp = less<>>
using ordered_set = tree<T, null_type , comp , rb_tree_tag , tree_order_statistics_node_update>;
#define V vector
#define rmin(a, b) a = min(a, b)
#define rmax(a, b) a = max(a, b)
#define rep(i, lim) for (int i = 0; i < (lim); i++)
#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
#define repv(i, v) for (auto &i : (v))
#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
#define sortv(v) sort(v.begin(), v.end())
#define all(v) (v).begin(), (v).end()
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;
template<class v>
auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
os << vec[0];
for (size_t i = 1; i < vec.size(); i++) {
os << ' ' << vec[i];
}
os << '\n';
return os;
}
template<class v>
auto operator>>(istream &is, vector<v> &vec)->istream& {
for (auto &i : vec) {
is >> i;
}
return is;
}
template<class v>
auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
for (auto &i : vec) {
os << i[0];
for (size_t j = 1; j < i.size(); j++) {
os << ' ' << i[j];
}
os << '\n';
}
return os;
}
template<class v>
auto operator>>(istream &is, vector<vector<v>> &vec)->istream& {
for (auto &i : vec) {
for (auto &j : i) {
is >> j;
}
}
return is;
}
const int oo = INT32_MAX >> 1;
const ll OO = INT64_MAX >> 1;
void pre()
{
}
#define TEST 1
void solve()
{
int n;
string s;
cin >> n >> s;
vi divs;
auto getdivs = [&]() {
for (int i = 1; i * i <= n; i++) {
if (n % i == 0) {
divs.push_back(i);
if (i * i != n) {
divs.push_back(n / i);
}
}
}
};
getdivs();
sortv(divs);
string cur;
V<bool> diff;
repv(d, divs) {
fill(all(diff), false);
while (cur.size() < d) {
cur.push_back(s[cur.size()]);
diff.emplace_back();
}
int j = 0;
int c = 0;
rep(i, n) {
if (cur[j] != s[i]) {
diff[j] = true;
c++;
}
j = (j + 1) * (j < d - 1);
}
if (c <= 1) {
cout << d << '\n';
return;
}
if (c == n / d - 1) {
auto check = [&]() {
int choice = -1;
rep(i, d) {
if (diff[i]) {
if (choice != -1) {
return false;
}
choice = i;
}
}
char prev = cur[choice];
cur[choice] = s[choice + d];
int c = 0;
int j = 0;
rep(i, n) {
if (cur[j] != s[i]) {
c++;
}
j = (j + 1) * (j < d - 1);
}
cur[choice] = prev;
return c == 1;
};
if (check()) {
cout << d << '\n';
return;
}
}
}
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(nullptr);
pre();
int t;
(TEST && cin >> t) || (t = 1);
while (t--) {
solve();
}
}