#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define faster ios_base :: sync_with_stdio(false) ; cin.tie(0) ; cout.tie(0) ;
#define endl '\n'
#define ll long long
const int maxn = 5e4 + 6;
template<class T> bool maximize(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
using namespace std;
using namespace __gnu_pbds;
const int base = 311;
int n;
basic_string<int> edges[maxn];
int ans = 1;
char a[maxn];
gp_hash_table<ll , bool> m;
struct Hash{
ll pw[maxn] , hash_val[maxn] , pre_hash[maxn];
int n ;
void prepare(int sz)
{
n = 0;
pw[0] = 1;
for (int i = 1 ; i <= sz ; ++i)
pw[i] = pw[i - 1] * base;
}
void push(char c)
{
n++;
hash_val[n] = hash_val[n - 1] * base + c;
pre_hash[n] = pre_hash[n - 1] + c * pw[n - 1];
}
void pop()
{
n--;
}
void clear()
{
n = 0;
}
bool IsPalin(int l)
{
return hash_val[l] == pre_hash[l];
}
ll get(int l)
{
return hash_val[n] - hash_val[n - l] * pw[l];
}
} hs;
struct CD{
int sz[maxn];
bool del[maxn];
void init()
{
memset(del , 0 , sizeof del);
}
void dfs(int u , int p)
{
sz[u] = 1;
for (int v : edges[u])
if (v != p && del[v] == 0)
{
dfs(v , u);
sz[u] += sz[v];
}
}
int find_centroid(int u , int p)
{
for (int v : edges[u])
if (v != p)
if (sz[v] > n / 2 && del[v] == 0)
return find_centroid(v , u);
return u;
}
bool get(int u , int p , int hight , int len)
{
hs.push(a[u]);
if (2 * hight <= len && m[hs.get(hight)]) return 1;
if (hight == len && hs.IsPalin(len)) return 1;
for (int v : edges[u])
if (v != p && del[v] == 0)
{
if (get(v , u , hight + 1 , len)) return 1;
}
hs.pop();
return 0;
}
bool update(int u , int p , int hight , int len)
{
hs.push(a[u]);
if (hight * 2 >= len && hs.IsPalin(hight * 2 - len))
m[hs.get(len - hight)] = 1;
if (hight == len && hs.IsPalin(len)) return 1;
for (int v : edges[u])
if (v != p && del[v] == 0)
{
if (update(v , u , hight + 1 , len)) return 1;
}
hs.pop();
return 0;
}
bool decompose(int u , int len)
{
dfs(u , 0);
int c = find_centroid(u , 0);
del[c] = 1;
m.clear();
for (int v : edges[c])
if (del[v] == 0)
{
hs.clear();
if (get(v , c , 1 , len)) return 1;
hs.clear();
hs.push(a[c]);
if (update(v , c , 2 , len)) return 1;
}
m.clear();
for (int i = edges[c].size() - 1 ; i >= 0 ; --i)
{
int v = edges[c][i];
if (del[v] == 0)
{
hs.clear();
if (get(v , c , 1 , len)) return 1;
hs.clear();
hs.push(a[c]);
if (update(v , c , 2 , len)) return 1;
}
}
for (int v : edges[u])
if (del[v] == 0)
{
if (decompose(v , len)) return 1;
}
return 0;
}
} cd;
void tknp(int l , int r, int ok)
{
while (l <= r )
{
int mid = l + r >> 1;
cd.init();
if (cd.decompose(1 , 2 * mid + ok)) maximize(ans , 2 * mid + ok ) , l = mid + 1;
else r = mid - 1;
}
}
void solve()
{
cin >> n ;
hs.prepare(n + 1);
for (int i = 1 ; i <= n ; ++i) cin >> a[i];
for (int i = 1 ; i < n ; ++i)
{
int u , v ; cin >> u >> v;
edges[u].push_back(v);
edges[v].push_back(u);
}
tknp(1 , n >> 1 , 0);
tknp(1 , n >> 1 , 1);
cout << ans << endl;
}
int32_t main()
{
faster;
// file("txt");
// int t ; cin >> t ; while (t--)
solve();
return 0;
}
Compilation message
lampice.cpp: In function 'void tknp(int, int, int)':
lampice.cpp:215:25: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
215 | int mid = l + r >> 1;
| ~~^~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
2 ms |
1880 KB |
Output is correct |
| 2 |
Correct |
3 ms |
2140 KB |
Output is correct |
| 3 |
Correct |
53 ms |
2336 KB |
Output is correct |
| 4 |
Correct |
55 ms |
2212 KB |
Output is correct |
| 5 |
Correct |
1 ms |
1880 KB |
Output is correct |
| 6 |
Correct |
1 ms |
1880 KB |
Output is correct |
| 7 |
Correct |
1 ms |
2040 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Execution timed out |
5076 ms |
8028 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Execution timed out |
5037 ms |
8912 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
2 ms |
1880 KB |
Output is correct |
| 2 |
Correct |
3 ms |
2140 KB |
Output is correct |
| 3 |
Correct |
53 ms |
2336 KB |
Output is correct |
| 4 |
Correct |
55 ms |
2212 KB |
Output is correct |
| 5 |
Correct |
1 ms |
1880 KB |
Output is correct |
| 6 |
Correct |
1 ms |
1880 KB |
Output is correct |
| 7 |
Correct |
1 ms |
2040 KB |
Output is correct |
| 8 |
Execution timed out |
5076 ms |
8028 KB |
Time limit exceeded |
| 9 |
Halted |
0 ms |
0 KB |
- |
