#include <bits/stdc++.h>
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
using namespace std;
typedef long long ll;
typedef unsigned long long llu;
typedef pair<int, int> pii;
typedef pair<int, pii> piii;
typedef pair<ll, ll> pll;
typedef pair<ll, int> pli;
typedef pair<int, ll> pil;
typedef pair<string, int> psi;
typedef pair<char, int> pci;
typedef pair<int, char> pic;
const long double PI = 3.141592653589793238462643383279502884197;
int n;
const int B = 127;
const ll pr[2] = { 1000000009, 1000000021 };
ll rhq[50002][2];
int dh[50002][2];
int rh[50002][2];
int pal[50002];
vector<int> v[50002];
unordered_map<ll, int> um;
int rotn[50002];
char visit[50002];
char s[50002];
int ha, hb;
vector<int> road;
int len, flag, ans = 1;
int pre(int o, int pa) {
int ret = 1;
pal[o] = 0;
for (int i : v[o])
if (i != pa && !visit[i])
ret += pre(i, o);
return rotn[o] = ret;
}
int cent(int o, int pa, int cap) {
for (int i : v[o])
if (i != pa && !visit[i] && rotn[i] > cap)
return cent(i, o, cap);
return o;
}
void pl(int o, int pa, int di, int h1, int h2, int fl) {
h1 = (h1 + rhq[di][0] * s[o]) % pr[0];
h2 = (h2 + rhq[di][1] * s[o]) % pr[1];
ha = h1 * rhq[n - di][0] % pr[0];
hb = h2 * rhq[n - di][1] % pr[1];
um[ha * pr[1] + hb] += fl;
if (di < len) {
for (int i : v[o])
if (i != pa && !visit[i])
pl(i, o, di + 1, h1, h2, fl);
}
}
void preHash(int o, int pa, int di) {
dh[o][0] = (dh[pa][0] + rhq[di][0] * s[o]) % pr[0];
dh[o][1] = (dh[pa][1] + rhq[di][1] * s[o]) % pr[1];
rh[o][0] = (rh[pa][0] + rhq[n - di][0] * s[o]) % pr[0];
rh[o][1] = (rh[pa][1] + rhq[n - di][1] * s[o]) % pr[1];
if (rh[o][0] == dh[o][0] * rhq[n - di][0] % pr[0] &&
rh[o][1] == dh[o][1] * rhq[n - di][1] % pr[1])
pal[o] = 1;
if (di < len) {
for (int i : v[o])
if (i != pa && !visit[i])
preHash(i, o, di + 1);
}
}
void cal(int o, int pa, int di) {
road.push_back(o);
int p = 2 * di + 1 - len;
if (sz(road) > p && p >= 0 && pal[road[p]]) {
ha = (dh[o][0] - dh[road[p]][0] + pr[0]) * rhq[n - di][0] % pr[0];
hb = (dh[o][1] - dh[road[p]][1] + pr[1]) * rhq[n - di][1] % pr[1];
if (um.find(ha * pr[1] + hb) != um.end() && um[ha * pr[1] + hb] >= 1)
flag = 1;
}
if (di < len && !flag)
for (int i : v[o])
if (i != pa && !visit[i])
cal(i, o, di + 1);
road.pop_back();
}
void go(int o) {
pre(o, o);
int t = cent(o, o, rotn[o] / 2);
visit[t]++;
um.clear();
um[0] = 100000;
preHash(t, 50001, 0);
for (int i : v[t])
if (!visit[i])
pl(i, t, 1, 0, 0, 1);
road.push_back(t);
for (int i : v[t])
if (!visit[i] && !flag) {
pl(i, t, 1, 0, 0, -1);
cal(i, t, 1);
pl(i, t, 1, 0, 0, 1);
}
road.pop_back();
for (int i : v[t])
if (!visit[i] && !flag)
go(i);
visit[t]--;
}
int main() {
scanf("%d", &n);
scanf("%s", s);
rhq[0][0] = rhq[0][1] = 1;
for (int i = 1; i <= n; i++)
for (int j = 0; j < 2; j++)
rhq[i][j] = rhq[i - 1][j] * B % pr[j];
for (int i = 0; i < n - 1; i++) {
int a, b;
scanf("%d %d", &a, &b);
a--; b--;
v[a].push_back(b);
v[b].push_back(a);
}
int l = 1, r = (n - 1) / 2, mid;
while (l <= r) {
mid = (l + r) / 2;
flag = 0;
len = mid * 2 + 1;
go(0);
if (flag) l = mid + 1;
else r = mid - 1;
}
ans = max(ans, r * 2 + 1);
l = 1, r = n / 2;
while (l <= r) {
mid = (l + r) / 2;
flag = 0;
len = mid * 2;
go(0);
if (flag) l = mid + 1;
else r = mid - 1;
}
ans = max(ans, r * 2);
printf("%d", ans);
}
Compilation message
lampice.cpp: In function 'int main()':
lampice.cpp:133:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &n);
~~~~~^~~~~~~~~~
lampice.cpp:134:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%s", s);
~~~~~^~~~~~~~~
lampice.cpp:143:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d %d", &a, &b);
~~~~~^~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
10 ms |
1528 KB |
Output is correct |
| 2 |
Correct |
21 ms |
1528 KB |
Output is correct |
| 3 |
Correct |
69 ms |
1656 KB |
Output is correct |
| 4 |
Correct |
79 ms |
1656 KB |
Output is correct |
| 5 |
Correct |
5 ms |
1528 KB |
Output is correct |
| 6 |
Correct |
6 ms |
1528 KB |
Output is correct |
| 7 |
Correct |
6 ms |
1528 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5044 ms |
9620 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Execution timed out |
5052 ms |
8232 KB |
Time limit exceeded |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
10 ms |
1528 KB |
Output is correct |
| 2 |
Correct |
21 ms |
1528 KB |
Output is correct |
| 3 |
Correct |
69 ms |
1656 KB |
Output is correct |
| 4 |
Correct |
79 ms |
1656 KB |
Output is correct |
| 5 |
Correct |
5 ms |
1528 KB |
Output is correct |
| 6 |
Correct |
6 ms |
1528 KB |
Output is correct |
| 7 |
Correct |
6 ms |
1528 KB |
Output is correct |
| 8 |
Execution timed out |
5044 ms |
9620 KB |
Time limit exceeded |
| 9 |
Halted |
0 ms |
0 KB |
- |
