Submission #42099

#	Time	Username	Problem	Language	Result	Execution time	Memory
42099		RockyB	Palindromes (APIO14_palindrome)	C++14	100 / 100	639 ms	76524 KiB

palindrome

/// In The Name Of God
 
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
 
#include <bits/stdc++.h>
 
#define f first
#define s second
 
#define pb push_back
#define pp pop_back
#define mp make_pair
 
#define sz(x) (int)x.size()
#define sqr(x) ((x) * 1ll * (x))
#define all(x) x.begin(), x.end()
 
#define Kazakhstan ios_base :: sync_with_stdio(0), cin.tie(0), cout.tie(0);
 
#define nl '\n'
#define ioi exit(0);
 
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
 
const int N = (int)3e5 + 7;
const int inf = (int)1e9 + 7;
const int mod = (int)1e9 + 7;
const ll linf = (ll)1e18 + 7;
 
const int dx[] = {-1, 0, 1, 0, 1, -1, -1, 1};
const int dy[] = {0, 1, 0, -1, 1, -1, 1, -1};
 
using namespace std;
 
inline void add(int &x, int y) {
	x += y;
	if (x >= mod) x -= mod;
	if (x < 0) x += mod;
}
inline int sum(int x, int y) {
	add(x, y);
	return x;
}
inline int mult(int x, int y) {
	return x * 1ll * y % mod;
}
 
/*struct hashMap {
	static const int Sz = N * 10;
	int h[Sz], t[Sz];
	hashMap() {
		memset(h, 0, sizeof(h));
		memset(t, -1, sizeof(t));
	}
	int add(int x) {
		int mask = (ll)x << 16 % Sz;
		while (t[mask] != -1 && t[mask] != x) mask++;
		t[mask] = x;
		return ++h[mask];
	}
} cnt;*/
 
int n;
int p[N];
char s[N];
 
ll ans;
 
const int p1 = 997;
const int p2 = 2017;
 
struct hsh {
	#define hack pair <int, ull> 
	int len;
	hack h[N], dg[N];
	inline void init(char *x) {
		len = strlen(x + 1);
		dg[0] = {1, 1};
		dg[1] = {p1, p2};
		for (int i = 1; i <= len; i++) {
			h[i + 1].f = sum(mult(h[i].f, p1), x[i]);
			h[i + 1].s = h[i].s * p2 + x[i];
			dg[i + 1].f = mult(dg[i].f, p1);
			dg[i + 1].s = dg[i].s * p2;
		}
	}
	inline hack get(int l, int r) {
		return {sum(h[r + 1].f, -mult(h[l].f, dg[r - l + 1].f)), h[r + 1].s - h[l].s * dg[r - l + 1].s};
	}
} t, t1;
 
inline bool check(int l, int r) {
	return t.get(l, r) == t1.get(n - r + 1, n - l + 1);
}
 
int sz;
int pref[N];
 
vector <int> root;
vector <int> g[N];
 
struct HASH{
  inline ull operator()(const pair<int,ull>&x)const{
    return (x.f ^ (x.s << 32));
  }
};

unordered_map <hack, int, HASH> id;
inline void addOdd(int p, int len) {
	int last = 0;
	for (int i = len; i >= 1; i--) {
		if (id.count(t.get(p - i + 1, p + i - 1))) {
			if (last) g[id[t.get(p - i + 1, p + i - 1)]].pb(last);
			break;
		}	
		id[t.get(p - i + 1, p + i - 1)] = ++sz;
		if (last) g[sz].pb(last);
		last = sz;
		if (i == 1) root.pb(sz);
	}
	pref[id[t.get(p - len + 1, p + len - 1)]]++;
}
inline void addEven(int p, int len) {
	int last = 0;
	for (int i = len; i >= 1; i--) {
		if (id.count(t.get(p - i + 1, p + i))) {
			if (last) g[id[t.get(p - i + 1, p + i)]].pb(last);
			break;
		}	
		id[t.get(p - i + 1, p + i)] = ++sz;
		if (last) g[sz].pb(last);
		last = sz;
		if (i == 1) root.pb(sz);
	}
	pref[id[t.get(p - len + 1, p + len)]]++;
}
 
inline void dfs1(int v, int lvl) {
	for (auto to : g[v]) {
		dfs1(to, lvl + 1);
		pref[v] += pref[to];
	}
	ans = max(ans, (ll)pref[v] * (lvl * 2 - 1));
}
inline void dfs2(int v, int lvl) {
	for (auto to : g[v]) {
		dfs2(to, lvl + 1);
		pref[v] += pref[to];
	}
	ans = max(ans, (ll)pref[v] * lvl * 2);
}
 
int main() {
	#ifdef IOI2018
		freopen ("in.txt", "r", stdin);
		//freopen ("slow.out", "w", stdout);
	#endif
	Kazakhstan
	cin >> (s + 1);
	n = strlen(s + 1);
	t.init(s);
	reverse(s + 1, s + 1 + n);
	t1.init(s);
	reverse(s + 1, s + 1 + n);
	/// even
	id.max_load_factor(0.25);
	id.reserve(n << 1);
 
	for (int i = 1; i <= n; i++) {
		int l = 1, r = min(i, n - i), res = 0;
		while (l <= r) {
			int mid = l + r >> 1;
			if (check(i - mid + 1, i + mid)) res = mid, l = mid + 1;
			else r = mid - 1;
		}
		if (res) addEven(i, res);
	}
	for (auto it : root) {
		dfs2(it, 1);
	}
	/// odd
	root.clear();
	for (int i = 1; i <= n; i++) {
		int l = 1, r = min(i, n - i + 1), res = 1;
		while (l <= r) {
			int mid = l + r >> 1;
			if (check(i - mid + 1, i + mid - 1)) res = mid, l = mid + 1;
			else r = mid - 1;
		}
		addOdd(i, res);
	}
	for (auto it : root) {
		dfs1(it, 1);
	}
	cout << ans;
	ioi
}

Compilation message (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:175:16: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
    int mid = l + r >> 1;
                ^
palindrome.cpp:189:16: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
    int mid = l + r >> 1;
                ^

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