/*
$$$$$$$\ $$\ $$$$$$$\
$$ __$$\ \__| $$ __$$\
$$ | $$ | $$$$$$\ $$$$$$\ $$\ $$$$$$$\ $$ | $$ | $$$$$$\ $$$$$$\ $$$$$$$\ $$$$$$\
$$$$$$$\ |$$ __$$\ $$ __$$\ $$ |$$ _____|$$$$$$$\ | \____$$\ $$ __$$\ $$ _____|\____$$\
$$ __$$\ $$ / $$ |$$ | \__|$$ |\$$$$$$\ $$ __$$\ $$$$$$$ |$$ | \__|$$ / $$$$$$$ |
$$ | $$ |$$ | $$ |$$ | $$ | \____$$\ $$ | $$ |$$ __$$ |$$ | $$ | $$ __$$ |
$$$$$$$ |\$$$$$$ |$$ | $$ |$$$$$$$ |$$$$$$$ |\$$$$$$$ |$$ | \$$$$$$$\\$$$$$$$ |
\_______/ \______/ \__| \__|\_______/ \_______/ \_______|\__| \_______|\_______|
*/
#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";
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);
}
remove_hash(centroid, -1, 0);
FORA(nxt, e[centroid]){
if (is_centroid[nxt])
continue;
ret |= decompose(nxt, lenght);
}
//is_centroid[centroid] = 0;
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;
^~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
10 ms |
1656 KB |
Output is correct |
| 2 |
Correct |
21 ms |
1656 KB |
Output is correct |
| 3 |
Correct |
67 ms |
2044 KB |
Output is correct |
| 4 |
Correct |
85 ms |
1916 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 |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5077 ms |
34320 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5061 ms |
32724 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
10 ms |
1656 KB |
Output is correct |
| 2 |
Correct |
21 ms |
1656 KB |
Output is correct |
| 3 |
Correct |
67 ms |
2044 KB |
Output is correct |
| 4 |
Correct |
85 ms |
1916 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 |
Execution timed out |
5077 ms |
34320 KB |
Time limit exceeded |
| 9 |
Halted |
0 ms |
0 KB |
- |
