Submission #199371

#	Time	Username	Problem	Language	Result	Execution time	Memory
199371		Benq	Palindromes (APIO14_palindrome)	C++14	100 / 100	118 ms	75052 KiB

palindrome

#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef long double ld;
typedef double db; 
typedef string str; 

typedef pair<int,int> pi;
typedef pair<ll,ll> pl; 
typedef pair<ld,ld> pd; 
#define mp make_pair 
#define f first
#define s second

typedef vector<int> vi; 
typedef vector<ll> vl; 
typedef vector<ld> vd; 
typedef vector<str> vs; 
typedef vector<pi> vpi;
typedef vector<pl> vpl; 
typedef vector<pd> vpd; 

#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) (x).rbegin(), (x).rend() 
#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 

#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; // = (119<<23)+1
const int MX = 2e5+5;
const ll INF = 1e18; 
const ld PI = acos((ld)-1);
const int xd[4] = {1,0,-1,0}, yd[4] = {0,1,0,-1}; 

template<class T> bool ckmin(T& a, const T& b) { 
	return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { 
	return a < b ? a = b, 1 : 0; }
int pc(int x) { return __builtin_popcount(x); } 

#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
template <class T> using Tree = tree<T, null_type, less<T>, 
	rb_tree_tag, tree_order_statistics_node_update>; 
// change null_type for map
#define ook order_of_key
#define fbo find_by_order

void treeExample() {
	Tree<int> t, t2; t.insert(8);
	auto it = t.insert(10).f; assert(it == t.lb(9));
	assert(t.ook(10) == 1); assert(t.ook(11) == 2);
	assert(*t.fbo(0) == 8);
	t.join(t2); // assuming T < T2 or T > T2, merge t2 into t
}

namespace input {
	template<class T> void re(complex<T>& x);
	template<class T1, class T2> void re(pair<T1,T2>& p);
	template<class T> void re(vector<T>& a);
	template<class T, size_t SZ> void re(array<T,SZ>& a);

	template<class T> void re(T& x) { cin >> x; }
	void re(double& x) { string t; re(t); x = stod(t); }
	void re(ld& x) { string t; re(t); x = stold(t); }
	template<class T, class... Ts> void re(T& t, Ts&... ts) { 
		re(t); re(ts...); 
	}

	template<class T> void re(complex<T>& x) { T a,b; re(a,b); x = {a,b}; }
	template<class T1, class T2> void re(pair<T1,T2>& p) { re(p.f,p.s); }
	template<class T> void re(vector<T>& a) { F0R(i,sz(a)) re(a[i]); }
	template<class T, size_t SZ> void re(array<T,SZ>& a) { F0R(i,SZ) re(a[i]); }
}

using namespace input;

namespace output {
	void pr(int x) { cout << x; }
	void pr(long x) { cout << x; }
	void pr(ll x) { cout << x; }
	void pr(unsigned x) { cout << x; }
	void pr(unsigned long x) { cout << x; }
	void pr(unsigned long long x) { cout << x; }
	void pr(float x) { cout << x; }
	void pr(double x) { cout << x; }
	void pr(ld x) { cout << x; }
	void pr(char x) { cout << x; }
	void pr(const char* x) { cout << x; }
	void pr(const string& x) { cout << x; }
	void pr(bool x) { pr(x ? "true" : "false"); }
	template<class T> void pr(const complex<T>& x) { cout << x; }
	
	template<class T1, class T2> void pr(const pair<T1,T2>& x);
	template<class T> void pr(const T& x);
	
	template<class T, class... Ts> void pr(const T& t, const Ts&... ts) { 
		pr(t); pr(ts...); 
	}
	template<class T1, class T2> void pr(const pair<T1,T2>& x) { 
		pr("{",x.f,", ",x.s,"}"); 
	}
	template<class T> void pr(const T& x) { 
		pr("{"); // const iterator needed for vector<bool>
		bool fst = 1; for (const auto& a: x) pr(!fst?", ":"",a), fst = 0; 
		pr("}");
	}
	
	void ps() { pr("\n"); } // print w/ spaces
	template<class T, class... Ts> void ps(const T& t, const Ts&... ts) { 
		pr(t); if (sizeof...(ts)) pr(" "); ps(ts...); 
	}
	
	void pc() { pr("]\n"); } // debug w/ commas
	template<class T, class... Ts> void pc(const T& t, const Ts&... ts) { 
		pr(t); if (sizeof...(ts)) pr(", "); pc(ts...); 
	}
	#define dbg(x...) pr("[",#x,"] = ["), pc(x);
}

using namespace output;

namespace io {
	void setIn(string s) { freopen(s.c_str(),"r",stdin); }
	void setOut(string s) { freopen(s.c_str(),"w",stdout); }
	void setIO(string s = "") {
		ios_base::sync_with_stdio(0); cin.tie(0); // fast I/O
		// 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
	}
}

using namespace io;

struct mi {
	typedef decay<decltype(MOD)>::type T; 
 	/// don't silently convert to T
	T v; explicit operator T() const { return v; }
	mi() { v = 0; }
	mi(ll _v) { 
		v = (-MOD < _v && _v < MOD) ? _v : _v % MOD;
		if (v < 0) v += MOD;
	}
	friend bool operator==(const mi& a, const mi& b) { 
		return a.v == b.v; }
	friend bool operator!=(const mi& a, const mi& b) { 
		return !(a == b); }
	friend bool operator<(const mi& a, const mi& b) { 
		return a.v < b.v; }
	friend void re(mi& a) { ll x; re(x); a = mi(x); }
	friend void pr(const mi& a) { pr(a.v); }
	friend ostream& operator<<(ostream& os, const mi& a) { 
		return os << a.v; }
   
	mi& operator+=(const mi& m) { 
		if ((v += m.v) >= MOD) v -= MOD; 
		return *this; }
	mi& operator-=(const mi& m) { 
		if ((v -= m.v) < 0) v += MOD; 
		return *this; }
	mi& operator*=(const mi& m) { 
		v = (ll)v*m.v%MOD; return *this; }
	mi& operator/=(const mi& m) { return (*this) *= inv(m); }
	friend mi pow(mi a, ll p) {
		mi ans = 1; assert(p >= 0);
		for (; p; p /= 2, a *= a) if (p&1) ans *= a;
		return ans;
	}
	friend mi inv(const mi& a) { assert(a.v != 0); 
		return pow(a,MOD-2); }
		
	mi operator-() const { return mi(-v); }
	mi& operator++() { return *this += 1; }
	mi& operator--() { return *this -= 1; }
	friend mi operator+(mi a, const mi& b) { return a += b; }
	friend mi operator-(mi a, const mi& b) { return a -= b; }
	friend mi operator*(mi a, const mi& b) { return a *= b; }
	friend mi operator/(mi a, const mi& b) { return a /= b; }
};
typedef vector<mi> vmi;
typedef pair<mi,mi> pmi;
typedef vector<pmi> vpmi;

vector<vmi> comb;
void genComb(int SZ) {
	comb.assign(SZ,vmi(SZ)); comb[0][0] = 1;
	FOR(i,1,SZ) F0R(j,i+1) 
		comb[i][j] = comb[i-1][j]+(j?comb[i-1][j-1]:0);
}

mt19937 rng((uint32_t)chrono::steady_clock::now().time_since_epoch().count()); 

struct PalTree {
	static const int ASZ = 26;
	struct node {
		array<int,ASZ> to = array<int,ASZ>();
		int len, link, oc = 0;
		int slink = 0, diff = 0;
		array<int,2> seriesAns;
		node(int _len, int _link) : len(_len), link(_link) {}
	};
	str s; vector<array<int,2>> ans;
	vector<node> d;
	int last = 1;
	PalTree() { 
		s += '@'; ans.pb({0,MOD});
		d.eb(0,1); d.eb(-1,0); 
	}
	int getLink(int v) {
		while (s[sz(s)-d[v].len-2] != s.bk) v = d[v].link;
		return v;
	}
	void updAns() { // serial path has O(log n) vertices
		ans.pb({MOD,MOD});
		for (int v = last; d[v].len > 0; v = d[v].slink) {
			d[v].seriesAns = ans[sz(s)-1-(d[d[v].slink].len+d[v].diff)];
			if (d[v].diff == d[d[v].link].diff) 
				F0R(i,2) ckmin(d[v].seriesAns[i],d[d[v].link].seriesAns[i]);
			// previous oc of link[v] = start of last oc of v
			F0R(i,2) ckmin(ans.bk[i],d[v].seriesAns[i^1]+1);
		}
	}
	void addChar(char C) {
		s += C; int c = C-'a'; last = getLink(last);
		if (!d[last].to[c]) {
			d.eb(d[last].len+2,d[getLink(d[last].link)].to[c]);
			d[last].to[c] = sz(d)-1;
			auto& z = d.bk; z.diff = z.len-d[z.link].len;
			z.slink = z.diff == d[z.link].diff 
				? d[z.link].slink : z.link;
			// slink[v] = max suffix u of v such that 
			// diff[v] != diff[u]
		}
		last = d[last].to[c]; d[last].oc ++;
		updAns();
	}
	void numOc() { // # occurrences of each palindrome
		ROF(i,2,sz(d)) d[d[i].link].oc += d[i].oc;
	}
};
 
PalTree p;
 
int nor(int x) {
	return x == MOD ? -1 : x;
}

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
	str s; 
	// F0R(i,500) s += char('a'+(rand()%26));
	re(s); 
	trav(c,s) {
		p.addChar(c);
		// ps(nor(p.ans.bk[1]),nor(p.ans.bk[0]));
	}
	p.numOc(); ll ans = 0;
	FOR(i,2,sz(p.d)) ckmax(ans,(ll)p.d[i].len*p.d[i].oc);
	ps(ans);
}
 
/* Look for:
* the exact constraints (multiple sets are too slow for n=10^6 :( ) 
* special cases (n=1?)
* overflow (ll vs int?)
* array bounds
*/

Compilation message (stderr)

palindrome.cpp: In function 'void io::setIn(std::__cxx11::string)':
palindrome.cpp:139:32: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  void setIn(string s) { freopen(s.c_str(),"r",stdin); }
                         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
palindrome.cpp: In function 'void io::setOut(std::__cxx11::string)':
palindrome.cpp:140:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
  void setOut(string s) { freopen(s.c_str(),"w",stdout); }
                          ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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