oj.uz

Submission #205048

# Submission time Handle Problem Language Result Execution time Memory
205048 2020-02-27T19:02:55 Z BorisBarca Lampice (COCI19_lampice) C++14
42 / 110
 5000 ms 11068 KB 
/*
$$$$$$$\                      $$\           $$$$$$$\
$$  __$$\                     \__|          $$  __$$\
$$ |  $$ | $$$$$$\   $$$$$$\  $$\  $$$$$$$\ $$ |  $$ | $$$$$$\   $$$$$$\   $$$$$$$\ $$$$$$\
$$$$$$$\ |$$  __$$\ $$  __$$\ $$ |$$  _____|$$$$$$$\ | \____$$\ $$  __$$\ $$  _____|\____$$\
$$  __$$\ $$ /  $$ |$$ |  \__|$$ |\$$$$$$\  $$  __$$\  $$$$$$$ |$$ |  \__|$$ /      $$$$$$$ |
$$ |  $$ |$$ |  $$ |$$ |      $$ | \____$$\ $$ |  $$ |$$  __$$ |$$ |      $$ |     $$  __$$ |
$$$$$$$  |\$$$$$$  |$$ |      $$ |$$$$$$$  |$$$$$$$  |\$$$$$$$ |$$ |      \$$$$$$$\\$$$$$$$ |
\_______/  \______/ \__|      \__|\_______/ \_______/  \_______|\__|       \_______|\_______|
*/
#include <bits/stdc++.h>

using namespace std;

#define PB push_back
#define MP make_pair
#define INS insert
#define LB lower_bound
#define UB upper_bound
#define pii pair <int,int>
#define pll pair <long long, long long>
#define si pair<string, int>
#define is pair<int, string>
#define X first
#define Y second
#define _ << " " <<
#define sz(x) (int)x.size()
#define all(a) (a).begin(),(a).end()
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORD(i, a, b) for (int i = (a); i > (b); --i)
#define FORR(i, l, r) for (int i = (l); i <= (r); ++i)
#define FORP(i, a, b) for ((i) = (a); (i) < (b); ++i)
#define FORA(i, x) for (auto &i : x)
#define REP(i, n) FOR(i, 0, n)
#define BITS(x) __builtin_popcount(x)
#define MSET memset
#define MCPY memcpy
#define SQ(a) (a) * (a)
#define TRACE(x) cout << #x " = " << (x) << '\n';
#define YES cout << "YES\n"
#define NO cout << "NO\n"

typedef long long ll;
typedef long double ld;
typedef vector <int> vi;
typedef vector <pii> vpi;
typedef vector <ll> vll;
typedef vector <pll> vpl;
typedef vector <double> vd;
typedef vector <ld> vld;
typedef vector<si> vsi;
typedef vector<is> vis;
typedef vector<string> vs;
//((float) t)/CLOCKS_PER_SEC

const int MOD = 1e9 + 7;
const double PI = acos(-1);
const int INF = 1e9 + 10;
const ll INFL = 1e18 + 10;
const int ABC = 30;
const int dx[] = {-1, 1, 0, 0};
const int dy[] = {0, 0, -1, 1};
const int dox[] = {-1, 1, 0, 0, -1, -1, 1, 1};
const int doy[] = {0, 0, -1, 1, -1, 1, -1, 1};

inline int sum(int a, int b){
	if (a + b < 0)
		return (a + b + MOD) % MOD;
	return (a + b) % MOD;
}

inline void add(int &a, int b){
	a = sum(a, b);
}

inline int mul(int a, int b){
	return (ll)a * (ll)b % MOD;
}

inline int sub(int a, int b){
	return (a - b + MOD) % MOD;
}

inline int fast_pot(ll pot, int n){
	ll ret = 1;
	while (n){
		if (n & 1)
			ret = (ret * pot) % MOD;
			pot = (pot * pot) % MOD;
			n >>= 1;
		}
	return ret;
}

inline int divide(int a, int b){
	return mul(a, fast_pot(b, MOD - 2));
}

ll lcm(ll a, ll b){
	return abs(a * b) / __gcd(a, b);
}

inline double ccw(pii A, pii B, pii C){
	return (A.X * B.Y) - (A.Y * B.X) + (B.X * C.Y) - (B.Y * C.X) + (C.X * A.Y) - (C.Y * A.X);
}

inline int CCW(pii A, pii B, pii C){
	double val = ccw(A, B, C);
	double eps = max(max(abs(A.X), abs(A.Y)), max(max(abs(B.X), abs(B.Y)), max(abs(C.X), abs(C.Y)))) / 1e9;
	if (val <= -eps)
		return -1;
	if (val >= eps)
		return 1;
	return 0;
}

void to_upper(string &x){
	REP(i, sz(x))
		x[i] = toupper(x[i]);
}

void to_lower(string &x){
	REP(i, sz(x))
		x[i] = tolower(x[i]);
}

string its(ll x){
	if (x == 0)
		return "0";
	string ret = "";
	while (x > 0){
		ret += (x % 10) + '0';
		x /= 10;
	}
	reverse(all(ret));
	return ret;
}

ll sti(string s){
	ll ret = 0;
	REP(i, sz(s)){
		ret *= 10;
		ret += (s[i] - '0');
	}
	return ret;
}

const int N = 5e4 + 10;
const int P = 31;

int n, up[N], down[N], pot[N], sz[N], centroid, anc[N];
string s;
vi e[N];
bool is_centroid[N];
map <pii, int> cnt;

void precompute(){
	pot[0] = 1;
	FOR(i, 1, n + 1)
		pot[i] = mul(pot[i - 1], P);
}

void dfs(int node, int dad){
	sz[node] = 1;
	FORA(nxt, e[node]){
		if (nxt == dad || is_centroid[nxt])
			continue;
		dfs(nxt, node);
		sz[node] += sz[nxt];
	}
}

void find_centroid(int node, int dad, int component_size){
	int maxi = component_size - sz[node];
	FORA(nxt, e[node]){
		if (nxt == dad || is_centroid[nxt])
			continue;
		maxi = max(maxi, sz[nxt]);
		find_centroid(nxt, node, component_size);
	}
	if (maxi <= component_size / 2)
		centroid = node;
}

void calc_hash(int node, int dad, int h_down, int h_up, int dep){
	down[node] = sum(mul(h_down, P), s[node] - 'a' + 1);
	up[node] = sum(h_up, mul(pot[dep], s[node] - 'a' + 1));

	FORA(nxt, e[node])
		if (!is_centroid[nxt] && nxt != dad)
			calc_hash(nxt, node, down[node], up[node], dep + 1);
}

void add_hash(int node, int dad, int dep){
	cnt[{dep, down[node]}]++;
	//cout << "ADD: " << dep _ down[node] << '\n';
	FORA(nxt, e[node])
		if (nxt != dad && !is_centroid[nxt])
			add_hash(nxt, node, dep + 1);
}

void remove_hash(int node, int dad, int dep){
	cnt[{dep, down[node]}]--;
	//cout << "REMOVE: " << dep _ down[node] << '\n';
	FORA(nxt, e[node])
		if (nxt != dad && !is_centroid[nxt])
			remove_hash(nxt, node, dep + 1);
}

bool solve(int node, int dad, int dep, int lenght){
	anc[dep] = node;
	if (dep == lenght - 1){
		if (up[node] == down[node])
			return 1;
	} else {
		int dep_b = (lenght - (dep + 1));
		if (dep_b <= dep && dep_b >= 0){
			if (dep == dep_b){
				//cout << "Q1" _ node + 1 _ dep_b << '\n';
				if (cnt[{dep_b, down[node]}])
					return 1;
			} else {
				int c = anc[dep - (dep_b + 1)];
				//cout << "Q2" _ node + 1 _ c + 1 _ dep_b << '\n';
				if (down[anc[dep - (dep_b + 1) + 1]] == up[anc[dep - (dep_b + 1) + 1]]){
					int h = sub(down[node], mul(pot[dep_b + 1], down[c]));
					if (cnt[{dep_b, h}])
						return 1;
				}
			}
		}
	}

	bool ret = 0;
	FORA(nxt, e[node])
		if (nxt != dad && !is_centroid[nxt])
			ret |= solve(nxt, node, dep + 1, lenght);
	return ret;
}	

bool decompose(int node, int lenght){
	if (lenght == 1)
		return 1;
	dfs(node, -1);
	if (sz[node] < lenght)
		return 0;

	//cout << "-----------\n";
	cnt.clear();

	find_centroid(node, -1, sz[node]);
	calc_hash(centroid, -1, 0, 0, 0);
	is_centroid[centroid] = 1;	

	add_hash(centroid, -1, 0);
	bool ret = 0;
	FORA(nxt, e[centroid]){
		if (is_centroid[nxt])
			continue;
		anc[0] = centroid;
		remove_hash(nxt, centroid, 1);
		//cout << nxt + 1 << '\n';
		ret |= solve(nxt, centroid, 1, lenght);
		add_hash(nxt, centroid, 1);
	}

	FORA(nxt, e[centroid]){
		if (is_centroid[nxt])
			continue;
		ret |= decompose(nxt, lenght);
	}

	return ret;
}

int parni(){
	int lo = 0, hi = n;
	while (lo < hi){
		int mid = (lo + hi + 1) / 2;
		memset(is_centroid, 0, sizeof is_centroid);
		if (decompose(1, 2 * mid))
			lo = mid;
		else
			hi = mid - 1;
	}
	return 2 * lo;
}

int neparni(){
	int lo = 0, hi = n;
	while (lo < hi){
		int mid = (lo + hi + 1) / 2;
		memset(is_centroid, 0, sizeof is_centroid);
		if (decompose(1, 2 * mid + 1))
			lo = mid;
		else
			hi = mid - 1;
	}
	return 2 * lo + 1;
}

int main () {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	
	cin >> n >> s;
	REP(i, n - 1){
		int x, y; cin >> x >> y;
		x--, y--;
		e[x].PB(y);
		e[y].PB(x);
	}

	precompute();

	cout << max(parni(), neparni()) << '\n';

	return 0;
}

Compilation message

lampice.cpp: In function 'int fast_pot(ll, int)':
lampice.cpp:87:3: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
   if (n & 1)
   ^~
lampice.cpp:89:4: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
    pot = (pot * pot) % MOD;
    ^~~

Subtask #1
17.0 / 17.0

# Verdict Execution time Memory Grader output
1 Correct 9 ms 1656 KB Output is correct
2 Correct 19 ms 1656 KB Output is correct
3 Correct 55 ms 1784 KB Output is correct
4 Correct 65 ms 1656 KB Output is correct
5 Correct 5 ms 1528 KB Output is correct
6 Correct 5 ms 1528 KB Output is correct
7 Correct 5 ms 1528 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 3871 ms 9208 KB Output is correct
2 Correct 1251 ms 9948 KB Output is correct
3 Correct 1014 ms 10104 KB Output is correct
4 Correct 1043 ms 10616 KB Output is correct
5 Correct 1614 ms 11068 KB Output is correct
6 Correct 384 ms 9464 KB Output is correct

Subtask #3
0 / 31.0

# Verdict Execution time Memory Grader output
1 Execution timed out 5094 ms 8016 KB Time limit exceeded
2 Halted 0 ms 0 KB -

Subtask #4
0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 9 ms 1656 KB Output is correct
2 Correct 19 ms 1656 KB Output is correct
3 Correct 55 ms 1784 KB Output is correct
4 Correct 65 ms 1656 KB Output is correct
5 Correct 5 ms 1528 KB Output is correct
6 Correct 5 ms 1528 KB Output is correct
7 Correct 5 ms 1528 KB Output is correct
8 Correct 3871 ms 9208 KB Output is correct
9 Correct 1251 ms 9948 KB Output is correct
10 Correct 1014 ms 10104 KB Output is correct
11 Correct 1043 ms 10616 KB Output is correct
12 Correct 1614 ms 11068 KB Output is correct
13 Correct 384 ms 9464 KB Output is correct
14 Execution timed out 5094 ms 8016 KB Time limit exceeded
15 Halted 0 ms 0 KB -