#include<bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 5e4 + 5;
const int mod = 1e9 + 7;
const int base = 31;
int n, sz[N], Pow[N];
string s;
vector<int> g[N];
bool del[N];
unordered_map<int, bool> mp[N];
int mx, centroid;
int dfs_size(int u, int p = 0) {
sz[u] = 1;
for(int v : g[u]) if(v != p && !del[v]) {
sz[u] += dfs_size(v, u);
}
return sz[u];
}
int find_centroid(int u, int p, int num) {
for(int v : g[u]) if(v != p && !del[v] && sz[v] > num / 2) return find_centroid(v, u, num);
return u;
}
void dfs_centroid(int u, int p, bool upd, int dep, int up, int down, int len, bool &found) {
mx = max(mx, dep);
up = ((ll) up * base + (s[u] - 'a' + 1)) % mod;
down = (down + (ll) Pow[dep - 1] * (s[u] - 'a' + 1)) % mod;
int val = ((ll) down * Pow[len - dep] - up) % mod; if(val < 0) val += mod;
if(upd) mp[dep][val] = 1;
else {
if(dep + 1 == len && up == ((ll) down * base + s[centroid] - 'a' + 1) % mod) {
found = 1;
return;
}
if(dep < len && mp[len - dep - 1][val]) {
found = 1;
return;
}
}
if(dep < len) {
for(int v : g[u]) if(v != p && !del[v])
dfs_centroid(v, u, upd, dep + 1, up, down, len, found);
if(found) return;
}
}
void calc(int u, int len, bool &found) {
centroid = find_centroid(u, 0, dfs_size(u));
del[centroid] = 1;
mx = 1;
for(int v : g[centroid]) if(!del[v]) {
dfs_centroid(v, centroid, 0, 1, s[centroid] - 'a' + 1, 0, len, found);
if(found) return;
dfs_centroid(v, centroid, 1, 1, s[centroid] - 'a' + 1, 0, len, found);
}
for(int i = 0; i <= mx; ++i) mp[i].clear();
for(int v : g[centroid]) if(!del[v]) {
calc(v, len, found);
if(found) return;
}
}
bool check(int len) {
for(int i = 1; i <= n; ++i) mp[i].clear();
memset(del, 0, sizeof(del));
bool found = 0;
calc(1, len, found);
return found;
}
void solve() {
cin >> n >> s; s = ' ' + s;
Pow[0] = 1; for(int i = 1; i <= n; ++i) Pow[i] = ((ll) Pow[i - 1] * i) % mod;
for(int i = 1, u, v; i < n; ++i) {
cin >> u >> v;
g[u].push_back(v);
g[v].push_back(u);
}
int ans = 0;
for(int i = 0; i < 2; ++i) {
int l = 0, r = n / 2 + 1, res = 0;
while(r - l > 1) {
int m = l + r >> 1;
if(check(i + 2 * m)) res = i + 2 * m, l = m;
else r = m;
}
ans = max(ans, res);
}
cout << ans << '\n';
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int test = 1;
// cin >> test;
while(test--) solve();
return 0;
}
// https://oj.uz/problem/view/COCI19_lampice
Compilation message
lampice.cpp: In function 'void dfs_centroid(int, int, bool, int, int, int, int, bool&)':
lampice.cpp:45:27: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
45 | for(int v : g[u]) if(v != p && !del[v])
| ^~
lampice.cpp:47:13: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the 'if'
47 | if(found) return;
| ^~
lampice.cpp: In function 'void solve()':
lampice.cpp:88:23: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
88 | int m = l + r >> 1;
| ~~^~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
4700 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
1612 ms |
29744 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3371 ms |
40280 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
3 ms |
4700 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
