#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
using str = string; // yay python!
using pi = pair<int,int>;
using pl = pair<ll,ll>;
using pd = pair<db,db>;
using vi = vector<int>;
using vb = vector<bool>;
using vl = vector<ll>;
using vd = vector<db>;
using vs = vector<str>;
using vpi = vector<pi>;
using vpl = vector<pl>;
using vpd = vector<pd>;
#define tcT template<class T
#define tcTU tcT, class U
// ^ lol this makes everything look weird but I'll try it
tcT> using V = vector<T>;
tcT, size_t SZ> using AR = array<T,SZ>;
tcT> using PR = pair<T,T>;
// pairs
#define mp make_pair
#define f first
#define s second
// vectors
#define sz(x) (int)(x).size()
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(), (x).rend()
#define sor(x) sort(all(x))
#define rsz resize
#define ins insert
#define ft front()
#define bk back()
#define pf push_front
#define pb push_back
#define eb emplace_back
#define lb lower_bound
#define ub upper_bound
// loops
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)
const int MOD = 1e9+7; // 998244353;
const int MX = 2e5+5;
const ll INF = 1e18; // not too close to LLONG_MAX
const ld PI = acos((ld)-1);
const int dx[4] = {1,0,-1,0}, dy[4] = {0,1,0,-1}; // for every grid problem!!
mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count());
template<class T> using pqg = priority_queue<T,vector<T>,greater<T>>;
// helper funcs
constexpr int pct(int x) { return __builtin_popcount(x); } // # of bits set
constexpr int bits(int x) { return 31-__builtin_clz(x); } // floor(log2(x))
ll cdiv(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
ll fdiv(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down
tcT> bool ckmin(T& a, const T& b) {
return b < a ? a = b, 1 : 0; } // set a = min(a,b)
tcT> bool ckmax(T& a, const T& b) {
return a < b ? a = b, 1 : 0; }
tcTU> T fstTrue(T lo, T hi, U f) {
hi ++; assert(lo <= hi); // assuming f is increasing
while (lo < hi) { // find first index such that f is true
T mid = lo+(hi-lo)/2;
f(mid) ? hi = mid : lo = mid+1;
}
return lo;
}
tcTU> T lstTrue(T lo, T hi, U f) {
lo --; assert(lo <= hi); // assuming f is decreasing
while (lo < hi) { // find first index such that f is true
T mid = lo+(hi-lo+1)/2;
f(mid) ? lo = mid : hi = mid-1;
}
return lo;
}
tcT> void remDup(vector<T>& v) { // sort and remove duplicates
sort(all(v)); v.erase(unique(all(v)),end(v)); }
tcTU> void erase(T& t, const U& u) { // don't erase
auto it = t.find(u); assert(it != end(t));
t.erase(u); } // element that doesn't exist from (multi)set
// INPUT
#define tcTUU tcT, class ...U
tcT> void re(complex<T>& c);
tcTU> void re(pair<T,U>& p);
tcT> void re(vector<T>& v);
tcT, size_t SZ> void re(AR<T,SZ>& a);
tcT> void re(T& x) { cin >> x; }
void re(db& d) { str t; re(t); d = stod(t); }
void re(ld& d) { str t; re(t); d = stold(t); }
tcTUU> void re(T& t, U&... u) { re(t); re(u...); }
tcT> void re(complex<T>& c) { T a,b; re(a,b); c = {a,b}; }
tcTU> void re(pair<T,U>& p) { re(p.f,p.s); }
tcT> void re(vector<T>& x) { trav(a,x) re(a); }
tcT, size_t SZ> void re(AR<T,SZ>& x) { trav(a,x) re(a); }
tcT> void rv(int& n, vector<T>& x) { re(n); x.rsz(n); trav(a,x) re(a); }
// TO_STRING
#define ts to_string
str ts(char c) { return str(1,c); }
str ts(const char* s) { return (str)s; }
str ts(str s) { return s; }
str ts(bool b) {
#ifdef LOCAL
return b ? "true" : "false";
#else
return ts((int)b);
#endif
}
tcT> str ts(complex<T> c) {
stringstream ss; ss << c; return ss.str(); }
str ts(vector<bool> v) {
str res = "{"; F0R(i,sz(v)) res += char('0'+v[i]);
res += "}"; return res; }
template<size_t SZ> str ts(bitset<SZ> b) {
str res = ""; F0R(i,SZ) res += char('0'+b[i]);
return res; }
tcTU> str ts(pair<T,U> p);
tcT> str ts(T v) { // containers with begin(), end()
#ifdef LOCAL
bool fst = 1; str res = "{";
for (const auto& x: v) {
if (!fst) res += ", ";
fst = 0; res += ts(x);
}
res += "}"; return res;
#else
bool fst = 1; str res = "";
for (const auto& x: v) {
if (!fst) res += " ";
fst = 0; res += ts(x);
}
return res;
#endif
}
tcTU> str ts(pair<T,U> p) {
#ifdef LOCAL
return "("+ts(p.f)+", "+ts(p.s)+")";
#else
return ts(p.f)+" "+ts(p.s);
#endif
}
// OUTPUT
tcT> void pr(T x) { cout << ts(x); }
tcTUU> void pr(const T& t, const U&... u) {
pr(t); pr(u...); }
void ps() { pr("\n"); } // print w/ spaces
tcTUU> void ps(const T& t, const U&... u) {
pr(t); if (sizeof...(u)) pr(" "); ps(u...); }
// DEBUG
void DBG() { cerr << "]" << endl; }
tcTUU> void DBG(const T& t, const U&... u) {
cerr << ts(t); if (sizeof...(u)) cerr << ", ";
DBG(u...); }
#ifdef LOCAL // compile with -DLOCAL, chk -> fake assert
#define dbg(...) cerr << "Line(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#define chk(...) if (!(__VA_ARGS__)) cerr << "Line(" << __LINE__ << ") -> function(" \
<< __FUNCTION__ << ") -> CHK FAILED: (" << #__VA_ARGS__ << ")" << "\n", exit(0);
#else
#define dbg(...) 0
#define chk(...) 0
#endif
// FILE I/O
void setIn(str s) { freopen(s.c_str(),"r",stdin); }
void setOut(str s) { freopen(s.c_str(),"w",stdout); }
void unsyncIO() { cin.tie(0)->sync_with_stdio(0); }
void setIO(str s = "") {
unsyncIO();
// cin.exceptions(cin.failbit);
// throws exception when do smth illegal
// ex. try to read letter into int
if (sz(s)) { setIn(s+".in"), setOut(s+".out"); } // for USACO
}
/**
* Description: Polynomial hash for substrings with two bases.
* Source:
* KACTL
* https://codeforces.com/contest/1207/submission/59309672
* Verification:
* USACO Dec 17 Plat 1 (LCP :o)
* CF Check Transcription
*/
typedef array<int,2> H; // bases not too close to ends
uniform_int_distribution<int> BDIST(0.1*MOD,0.9*MOD);
const H base = {BDIST(rng),BDIST(rng)};
/// const T ibase = {(int)inv(mi(base[0])),(int)inv(mi(base[1]))};
H operator+(H l, H r) {
F0R(i,2) if ((l[i] += r[i]) >= MOD) l[i] -= MOD;
return l; }
H operator-(H l, H r) {
F0R(i,2) if ((l[i] -= r[i]) < 0) l[i] += MOD;
return l; }
H operator*(H l, H r) {
F0R(i,2) l[i] = (ll)l[i]*r[i]%MOD;
return l; }
H makeH(char c) { return {c,c}; }
/// H& operator+=(H& l, H r) { return l = l+r; }
/// H& operator-=(H& l, H r) { return l = l-r; }
/// H& operator*=(H& l, H r) { return l = l*r; }
vector<H> pows = {{1,1}};
struct HashRange {
str S; vector<H> cum = {{0,0}};
void add(char c) { S += c; cum.pb(base*cum.bk+makeH(c)); }
void add(str s) { trav(c,s) add(c); }
void extend(int len) { while (sz(pows) <= len) pows.pb(base*pows.bk); }
H hash(int l, int r) { int len = r+1-l; extend(len);
return cum[r+1]-pows[len]*cum[l]; }
/**int lcp(HashRange& b) { return first_true([&](int x) {
return cum[x] != b.cum[x]; },0,min(sz(S),sz(b.S)))-1; }*/
};
/// HashRange HR; HR.add("ababab"); F0R(i,6) FOR(j,i,6) ps(i,j,HR.hash(i,j));
HashRange hr, hr_rev;
int N;
str W;
map<char,ll> ad[MX];
ll lin[MX], cons[MX];
ll ans;
H hash_nor(int l, int r) { return hr.hash(l,r); }
H hash_rev(int l, int r) { return hr_rev.hash(N-1-r,N-1-l); }
void sub_range(int l, int r) {
if (l > r) return;
auto add_linear = [&](int l, int r, int x) { lin[l] += x, lin[r] -= x; };
auto add_cons = [&](int l, int r, int x) { cons[l] += x, cons[r] -= x; };
add_linear(l,(l+r+1)/2,1);
add_cons (l,(l+r+1)/2,-(l-1));
add_linear((l+r+2)/2,r+1,-1);
add_cons ((l+r+2)/2,r+1,r+1);
// FOR(i,l,(l+r+1)/2) sub[i] += i-(l-1);
// FOR(i,(l+r+2)/2,r+1) sub[i] += r+1-i;
// int cnt = 0;
// while (l < r) {
// cnt ++;
// sub[l] += cnt, sub[r] += cnt;
// l ++, r --;
// }
}
void account(int l, int r) {
int mx = min(l,N-1-r);
int len = lstTrue(0,mx,[&](int x){
return hash_nor(l-x,r+x) == hash_rev(l-x,r+x);
});
ans += len + (l == r);
sub_range(l-len,r+len); // l-len to r+len is a palindrome
if (l-len > 0 && r+len < N-1) {
int new_len = lstTrue(len+2,mx,[&](int x){
return hash_nor(l-x,l-len-2) == hash_rev(r+len+2,r+x);
});
ad[l-len-1][W[r+len+1]] += new_len-len;
ad[r+len+1][W[l-len-1]] += new_len-len;
}
}
int main() {
setIO(); re(W); N = sz(W);
hr.add(W); reverse(all(W));
hr_rev.add(W); reverse(all(W));
F0R(i,N) account(i,i);
F0R(i,N-1) account(i+1,i);
FOR(i,1,N) lin[i] += lin[i-1], cons[i] += cons[i-1];
ll bes = 0;
F0R(i,N) trav(t,ad[i]) ckmax(bes,t.s-lin[i]*i-cons[i]);
ps(bes+ans);
}
/* stuff you should look for
* int overflow, array bounds
* special cases (n=1?)
* do smth instead of nothing and stay organized
* WRITE STUFF DOWN
* DON'T GET STUCK ON ONE APPROACH
*/
Compilation message
palinilap.cpp: In function 'void setIn(str)':
palinilap.cpp:185:28: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
185 | void setIn(str s) { freopen(s.c_str(),"r",stdin); }
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
palinilap.cpp: In function 'void setOut(str)':
palinilap.cpp:186:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
186 | void setOut(str s) { freopen(s.c_str(),"w",stdout); }
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
7 ms |
9708 KB |
Output is correct |
| 2 |
Correct |
6 ms |
9708 KB |
Output is correct |
| 3 |
Correct |
6 ms |
9708 KB |
Output is correct |
| 4 |
Correct |
6 ms |
9708 KB |
Output is correct |
| 5 |
Correct |
8 ms |
9836 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
10 ms |
10348 KB |
Output is correct |
| 2 |
Correct |
11 ms |
10348 KB |
Output is correct |
| 3 |
Correct |
12 ms |
10476 KB |
Output is correct |
| 4 |
Correct |
10 ms |
10348 KB |
Output is correct |
| 5 |
Correct |
13 ms |
10508 KB |
Output is correct |
| 6 |
Correct |
13 ms |
10476 KB |
Output is correct |
| 7 |
Correct |
15 ms |
11116 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
168 ms |
19960 KB |
Output is correct |
| 2 |
Correct |
129 ms |
20328 KB |
Output is correct |
| 3 |
Correct |
121 ms |
20436 KB |
Output is correct |
| 4 |
Correct |
178 ms |
25300 KB |
Output is correct |
| 5 |
Correct |
177 ms |
25432 KB |
Output is correct |
| 6 |
Correct |
177 ms |
25556 KB |
Output is correct |
| 7 |
Correct |
176 ms |
25560 KB |
Output is correct |
| 8 |
Correct |
86 ms |
15192 KB |
Output is correct |
| 9 |
Correct |
176 ms |
25556 KB |
Output is correct |
| 10 |
Correct |
175 ms |
25300 KB |
Output is correct |
| 11 |
Correct |
116 ms |
20312 KB |
Output is correct |
| 12 |
Correct |
170 ms |
20824 KB |
Output is correct |
| 13 |
Correct |
173 ms |
21064 KB |
Output is correct |
| 14 |
Correct |
180 ms |
26712 KB |
Output is correct |
| 15 |
Correct |
179 ms |
25556 KB |
Output is correct |
| 16 |
Correct |
155 ms |
26584 KB |
Output is correct |
| 17 |
Correct |
196 ms |
37204 KB |
Output is correct |
| 18 |
Correct |
174 ms |
20568 KB |
Output is correct |
| 19 |
Correct |
198 ms |
37308 KB |
Output is correct |
