/*************************************
* author: marvinthang *
* created: 27.11.2023 15:58:18 *
*************************************/
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define left ___left
#define right ___right
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define MASK(i) (1LL << (i))
#define BIT(x, i) ((x) >> (i) & 1)
#define __builtin_popcount __builtin_popcountll
#define ALL(v) (v).begin(), (v).end()
#define REP(i, n) for (int i = 0, _n = (n); i < _n; ++i)
#define REPD(i, n) for (int i = (n); i-- > 0; )
#define FOR(i, a, b) for (int i = (a), _b = (b); i < _b; ++i)
#define FORD(i, b, a) for (int i = (b), _a = (a); --i >= _a; )
#define FORE(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORDE(i, b, a) for (int i = (b), _a = (a); i >= _a; --i)
#define scan_op(...) istream & operator >> (istream &in, __VA_ARGS__ &u)
#define print_op(...) ostream & operator << (ostream &out, const __VA_ARGS__ &u)
#ifdef LOCAL
#include "debug.h"
#else
#define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
#define DB(...) 23
#define db(...) 23
#define debug(...) 23
#endif
template <class U, class V> scan_op(pair <U, V>) { return in >> u.first >> u.second; }
template <class T> scan_op(vector <T>) { for (size_t i = 0; i < u.size(); ++i) in >> u[i]; return in; }
template <class U, class V> print_op(pair <U, V>) { return out << '(' << u.first << ", " << u.second << ')'; }
template <size_t i, class T> ostream & print_tuple_utils(ostream &out, const T &tup) { if constexpr(i == tuple_size<T>::value) return out << ")"; else return print_tuple_utils<i + 1, T>(out << (i ? ", " : "(") << get<i>(tup), tup); }
template <class ...U> print_op(tuple<U...>) { return print_tuple_utils<0, tuple<U...>>(out, u); }
template <class Con, class = decltype(begin(declval<Con>()))> typename enable_if <!is_same<Con, string>::value, ostream&>::type operator << (ostream &out, const Con &con) { out << '{'; for (__typeof(con.begin()) it = con.begin(); it != con.end(); ++it) out << (it == con.begin() ? "" : ", ") << *it; return out << '}'; }
template <class A, class B> bool minimize(A &a, B b) { if (a > b) { a = b; return true; } return false; }
template <class A, class B> bool maximize(A &a, B b) { if (a < b) { a = b; return true; } return false; }
// end of template
const int BASE = 31;
void process(void) {
string s; cin >> s;
auto manacher_odd = [&] (string s) {
int n = s.size();
s = '$' + s + '^';
vector <int> p(n + 1);
int l = 1, r = 1;
FORE(i, 1, n) {
p[i] = max(0, min(r - i, p[l + r - i]));
while (s[i - p[i]] == s[i + p[i]]) ++p[i];
if (i + p[i] > r) r = i + p[i], l = i - p[i];
}
return vector(1 + ALL(p));
};
auto manacher = [&] (string s) {
string t;
for (char c: s) t += string("#") + c;
auto res = manacher_odd(t + "#");
for (int &x: res) x >>= 1;
return vector(1 + ALL(res) - 1);
};
auto pl = manacher(s);
s = s + '#';
int n = s.size();
vector <int> pos(n), cnt(n), lcp(n);
iota(ALL(pos), 0);
sort(ALL(pos), [&] (int a, int b) { return s[a] < s[b]; });
cnt[pos[0]] = 0;
FOR(i, 1, n) cnt[pos[i]] = cnt[pos[i - 1]] + (s[pos[i]] != s[pos[i - 1]]);
auto countSort = [&] (vector <int> &p, vector <int> &c) {
vector <int> pos(n), new_p(n);
for (int &x: c) if (x < n) ++pos[x + 1];
partial_sum(ALL(pos), pos.begin());
for (int &x: p) new_p[pos[c[x]]++] = x;
p = move(new_p);
};
for (int k = 1; k < n; k <<= 1) {
REP(i, n) {
pos[i] = pos[i] - k;
if (pos[i] < 0) pos[i] += n;
}
countSort(pos, cnt);
vector <int> new_c(n);
new_c[pos[0]] = 0;
pair <int, int> prv(cnt[pos[0]], cnt[pos[0] + k - (pos[0] + k < n ? 0 : n)]);
FOR(i, 1, n) {
pair <int, int> cur(cnt[pos[i]], cnt[pos[i] + k - (pos[i] + k < n ? 0 : n)]);
new_c[pos[i]] = new_c[pos[i - 1]] + (prv != cur);
prv = cur;
}
cnt = move(new_c);
}
for (int i = 0, k = 0; i < n - 1; ++i) {
int j = pos[cnt[i] - 1];
while (s[i + k] == s[j + k]) ++k;
lcp[cnt[i]] = k;
k = max(k - 1, 0);
}
vector <vector <int>> add_odd(n), add_even(n), del_odd(n), del_even(n);
REP(i, pl.size()) if (pl[i]) {
int p = i / 2;
if (i & 1) {
add_even[p - pl[i] + 1].push_back(p);
del_even[p + pl[i]].push_back(p);
} else {
add_odd[p - pl[i] + 1].push_back(p);
del_odd[p + pl[i] - 1].push_back(p);
}
}
set <int> ms_odd, ms_even;
vector <int> max_palin(n, 0);
REP(i, n - 1) {
for (int x: add_odd[i]) ms_odd.insert(x);
for (int x: add_even[i]) ms_even.insert(x);
// cout << add_odd[i] << '\n';
// cout << add_even[i] << '\n';
int upper = lcp[cnt[i]];
// (v - i) * 2 + 1 <= upper
// v <= (upper + 2i - 1) / 2
auto it = ms_odd.upper_bound((upper + 2 * i - 1) / 2);
if (it != ms_odd.begin()) maximize(max_palin[i], (*prev(it) - i) * 2 + 1);
// (i - v) * 2 + 1 <= upper
// v >= (2i - upper + 1) / 2
it = ms_odd.lower_bound((2 * i - upper + 2) / 2);
if (it != ms_odd.end()) maximize(max_palin[i], (i - *it) * 2 + 1);
// (v - i + 1) * 2 <= upper
// v <= (upper + 2i - 2) / 2
it = ms_even.upper_bound((upper + 2 * i - 2) / 2);
if (it != ms_even.begin()) maximize(max_palin[i], (*prev(it) - i + 1) * 2);
// (i - v) * 2 <= upper
// v >= (2i - upper) / 2
it = ms_even.lower_bound((2 * i - upper + 1) / 2);
if (it != ms_even.end()) maximize(max_palin[i], (i - *it) * 2);
for (int x: del_odd[i]) ms_odd.erase(x);
for (int x: del_even[i]) ms_even.erase(x);
// cout << "------------\n";
}
// cout << max_palin << '\n';
stack <int> st;
vector <int> left(n);
REP(i, n) {
while (!st.empty() && lcp[st.top()] >= lcp[i]) st.pop();
left[i] = st.empty() ? 0 : st.top();
st.push(i);
}
// cout << pos << '\n';
// cout << lcp << '\n';
while (!st.empty()) st.pop();
long long res = 0;
REP(i, pl.size()) maximize(res, pl[i] * 2 - !(i & 1));
REPD(i, n) {
while (!st.empty() && lcp[st.top()] >= lcp[i]) st.pop();
// cout << i << ' ' << pos[i] << ' ' << max_palin[pos[i]] << ' ' << left[i] << ' ' << (st.empty() ? n : st.top()) << '\n';
maximize(res, 1LL * ((st.empty() ? n : st.top()) - left[i]) * max_palin[pos[i]]);
st.push(i);
}
cout << res << '\n';
}
int main(void) {
ios_base::sync_with_stdio(false); cin.tie(nullptr); // cout.tie(nullptr);
file("palindrome");
// int t; cin >> t; while (t--)
process();
// cerr << "Time elapsed: " << TIME << " s.\n";
return (0^0);
}
Compilation message
palindrome.cpp: In function 'int main()':
palindrome.cpp:30:61: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
30 | #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:171:2: note: in expansion of macro 'file'
171 | file("palindrome");
| ^~~~
palindrome.cpp:30:94: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
30 | #define file(name) if (fopen(name".inp", "r")) { freopen(name".inp", "r", stdin); freopen(name".out", "w", stdout); }
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:171:2: note: in expansion of macro 'file'
171 | file("palindrome");
| ^~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
344 KB |
Output is correct |
| 2 |
Correct |
0 ms |
348 KB |
Output is correct |
| 3 |
Runtime error |
1 ms |
604 KB |
Execution killed with signal 6 |
| 4 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
1 ms |
604 KB |
Output is correct |
| 2 |
Correct |
1 ms |
604 KB |
Output is correct |
| 3 |
Correct |
1 ms |
456 KB |
Output is correct |
| 4 |
Correct |
1 ms |
604 KB |
Output is correct |
| 5 |
Correct |
1 ms |
604 KB |
Output is correct |
| 6 |
Correct |
1 ms |
604 KB |
Output is correct |
| 7 |
Correct |
1 ms |
604 KB |
Output is correct |
| 8 |
Correct |
1 ms |
600 KB |
Output is correct |
| 9 |
Correct |
1 ms |
604 KB |
Output is correct |
| 10 |
Correct |
1 ms |
604 KB |
Output is correct |
| 11 |
Correct |
1 ms |
604 KB |
Output is correct |
| 12 |
Correct |
1 ms |
604 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
6 ms |
2112 KB |
Output is correct |
| 2 |
Runtime error |
3 ms |
1344 KB |
Execution killed with signal 6 |
| 3 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
62 ms |
18180 KB |
Output is correct |
| 2 |
Correct |
57 ms |
17088 KB |
Output is correct |
| 3 |
Correct |
101 ms |
23984 KB |
Output is correct |
| 4 |
Correct |
91 ms |
22468 KB |
Output is correct |
| 5 |
Correct |
48 ms |
15888 KB |
Output is correct |
| 6 |
Correct |
52 ms |
16304 KB |
Output is correct |
| 7 |
Correct |
59 ms |
18344 KB |
Output is correct |
| 8 |
Runtime error |
14 ms |
6860 KB |
Execution killed with signal 6 |
| 9 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
205 ms |
53604 KB |
Output is correct |
| 2 |
Runtime error |
69 ms |
18780 KB |
Execution killed with signal 6 |
| 3 |
Halted |
0 ms |
0 KB |
- |
