Submission #647751

#	Time	Username	Problem	Language	Result	Execution time	Memory
647751		ghostwriter	회문 (APIO14_palindrome)	C++14	47 / 100	1083 ms	5388 KiB

palindrome

#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include <debug.h>
#else
#define debug(...)
#endif
#define ft front
#define bk back
#define st first
#define nd second
#define ins insert
#define ers erase
#define pb push_back
#define pf push_front
#define _pb pop_back
#define _pf pop_front
#define lb lower_bound
#define ub upper_bound
#define mtp make_tuple
#define bg begin
#define ed end
#define all(x) (x).bg(), (x).ed()
#define sz(x) (int)(x).size()
typedef long long ll; typedef unsigned long long ull;
typedef double db; typedef long double ldb;
typedef pair<int, int> pi; typedef pair<ll, ll> pll;
typedef vector<int> vi; typedef vector<ll> vll; typedef vector<pi> vpi; typedef vector<pll> vpll;
typedef string str;
template<typename T> T gcd(T a, T b) { return (b == 0? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
#define FOR(i, l, r) for (int (i) = (l); (i) <= (r); ++(i))
#define FOS(i, r, l) for (int (i) = (r); (i) >= (l); --(i))
#define FRN(i, n) for (int (i) = 0; (i) < (n); ++(i))
#define FSN(i, n) for (int (i) = (n) - 1; (i) >= 0; --(i))
#define EACH(i, x) for (auto &(i) : (x))
#define WHILE while
#define file "TEST"
mt19937 rd(chrono::steady_clock::now().time_since_epoch().count());
ll rand(ll l, ll r) { return uniform_int_distribution<ll>(l, r)(rd); }
/*
----------------------------------------------------------------
    END OF TEMPLATE
----------------------------------------------------------------
    Tran The Bao - ghostwriter
    Training for VOI23 gold medal
----------------------------------------------------------------
    DIT ME CHUYEN BAO LOC
----------------------------------------------------------------
*/
const int M = 1e9 + 9;
const int base = 37;
const int N = 3e5 + 2;
int n, sa[N], p[N], h[N], h1[N];
str s;
ll rs = 0;
// int geth(const int &l, const int &r) { return (h[r] - 1LL * h[l - 1] * p[r - l + 1] % M + M) % M; }
int geth1(const int &l, const int &r) { return (h1[l] - 1LL * h1[r + 1] * p[r - l + 1] % M + M) % M; }
#define geth(l, r) ((h[(r)] - 1LL * h[(l) - 1] * p[(r) - (l) + 1] % M + M) % M)
// #define geth1(l, r) ((h1[l] - 1LL * h1[r + 1] * p[r - l + 1] % M + M) % M)
int lcp(const int &a, const int &b) {
	int l = 1, r = min(n - a + 1, n - b + 1), ans = 0;
	WHILE(l <= r) {
		int mid = l + (r - l) / 2;
		if (geth(a, a + mid - 1) == geth(b, b + mid - 1)) {
			ans = mid;
			l = mid + 1;
		}
		else r = mid - 1;
	}
	return ans;
}
bool cmp(const int &a, const int &b) {
	int len = lcp(a, b);
	if (len == n - a + 1) return 1;
	if (len == n - b + 1) return 0;
	return s[a + len] < s[b + len];
}
signed main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    // freopen(file".inp", "r", stdin);
    // freopen(file".out", "w", stdout);
    cin >> s;
    n = sz(s);
    s = "#" + s + "#";
    p[0] = 1;
    FOR(i, 1, n) {
    	h[i] = (1LL * h[i - 1] * base % M + s[i] - 'a' + 1) % M;
    	p[i] = 1LL * p[i - 1] * base % M;
    	sa[i] = i;
    }
    FOS(i, n, 1) h1[i] = (1LL * h1[i + 1] * base % M + s[i] - 'a' + 1) % M;
    sort(sa + 1, sa + 1 + n, cmp);
    FOR(i, 1, n) {
    	int l = 1, r = min(i - 1, n - i), ans = 0;
    	WHILE(l <= r) {
    		int mid = l + (r - l) / 2;
    		if (geth(i - mid, i + mid) == geth1(i - mid, i + mid)) {
    			ans = mid;
    			l = mid + 1;
    		}
    		else r = mid - 1;
    	}
    	int nl = i - ans, nr = i + ans;
    	l = 1; r = n;
    	int lm = 0, rm = 0;
    	WHILE(l <= r) {
    		int mid = l + (r - l) / 2, cur = sa[mid];
    		int len = lcp(nl, cur);
    		if (len >= nr - nl + 1) {
    			lm = mid;
    			r = mid - 1;
    		}
    		else if (len == n - cur + 1) l = mid + 1;
    		else if (s[cur + len] < s[nl + len]) l = mid + 1;
    		else r = mid - 1;
    	}
    	l = 1; r = n;
    	WHILE(l <= r) {
    		int mid = l + (r - l) / 2, cur = sa[mid];
    		int len = lcp(nl, cur);
    		if (len >= nr - nl + 1) {
    			rm = mid;
    			l = mid + 1;
    		}
    		else if (len == n - cur + 1) l = mid + 1;
    		else if (s[cur + len] < s[nl + len]) l = mid + 1;
    		else r = mid - 1;
    	}
    	rs = max(rs, (2LL * ans + 1) * (rm - lm + 1));
    }
    FOR(i, 1, n - 1) {
    	if (s[i] != s[i + 1]) continue;
    	int l = 1, r = min(i - 1, n - i - 1), ans = 0;
    	WHILE(l <= r) {
    		int mid = l + (r - l) / 2;
    		if (geth(i - mid, i + 1 + mid) == geth1(i - mid, i + 1 + mid)) {
    			ans = mid;
    			l = mid + 1;
    		}
    		else r = mid - 1;
    	}
    	int nl = i - ans, nr = i + 1 + ans;
    	l = 1; r = n;
    	int lm = 0, rm = 0;
    	WHILE(l <= r) {
    		int mid = l + (r - l) / 2, cur = sa[mid];
    		int len = lcp(nl, cur);
    		if (len >= nr - nl + 1) {
    			lm = mid;
    			r = mid - 1;
    		}
    		else if (len == n - cur + 1) l = mid + 1;
    		else if (s[cur + len] < s[nl + len]) l = mid + 1;
    		else r = mid - 1;
    	}
    	l = 1; r = n;
    	WHILE(l <= r) {
    		int mid = l + (r - l) / 2, cur = sa[mid];
    		int len = lcp(nl, cur);
    		if (len >= nr - nl + 1) {
    			rm = mid;
    			l = mid + 1;
    		}
    		else if (len == n - cur + 1) l = mid + 1;
    		else if (s[cur + len] < s[nl + len]) l = mid + 1;
    		else r = mid - 1;
    	}
    	rs = max(rs, (2LL * ans + 2) * (rm - lm + 1));
    }
    cout << rs;
    return 0;
}
/*
----------------------------------------------------------------
From Benq:
    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 (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:32:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   32 | #define FOR(i, l, r) for (int (i) = (l); (i) <= (r); ++(i))
      |                               ^
palindrome.cpp:87:5: note: in expansion of macro 'FOR'
   87 |     FOR(i, 1, n) {
      |     ^~~
palindrome.cpp:33:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   33 | #define FOS(i, r, l) for (int (i) = (r); (i) >= (l); --(i))
      |                               ^
palindrome.cpp:92:5: note: in expansion of macro 'FOS'
   92 |     FOS(i, n, 1) h1[i] = (1LL * h1[i + 1] * base % M + s[i] - 'a' + 1) % M;
      |     ^~~
palindrome.cpp:32:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   32 | #define FOR(i, l, r) for (int (i) = (l); (i) <= (r); ++(i))
      |                               ^
palindrome.cpp:94:5: note: in expansion of macro 'FOR'
   94 |     FOR(i, 1, n) {
      |     ^~~
palindrome.cpp:32:31: warning: unnecessary parentheses in declaration of 'i' [-Wparentheses]
   32 | #define FOR(i, l, r) for (int (i) = (l); (i) <= (r); ++(i))
      |                               ^
palindrome.cpp:132:5: note: in expansion of macro 'FOR'
  132 |     FOR(i, 1, n - 1) {
      |     ^~~

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27