Submission #2009030
Source Code Expand
#include <cstdio>
#include <algorithm>
#include <vector>
#include <functional>
#include <cassert>
#include <map>
#include <iostream>
#include <set>
using namespace std;
const int MOD = 1e9 + 7;
const int N = 5000001;
long long fact[N];
long long invfact[N];
long long inv[N];
void init() {
fact[0] = fact[1] = 1;
for (int i = 2; i < N; i ++) fact[i] = fact[i - 1] * i % MOD;
inv[1] = 1;
for (int i = 2; i < N; i ++) inv[i] = (MOD - MOD / i) * inv[MOD % i] % MOD;
invfact[0] = invfact[1] = 1;
for (int i = 2; i < N; i ++) invfact[i] = invfact[i - 1] * inv[i] % MOD;
}
long long C(long long n, long long r) {
if (n < 0 || r < 0 || n < r) return 0;
return fact[n] * invfact[n - r] % MOD * invfact[r] % MOD;
}
vector<int> Centroid(int root, const vector<vector<int>> &g, const vector<bool> &dead) {
static vector<int> sz(g.size());
int alive_cnt = 0;
function<void (int, int)> count_alive = [&](int u, int prev) {
alive_cnt ++;
for (auto v : g[u]) if (v != prev && !dead[v]) {
count_alive(v, u);
}
};
count_alive(root, -1);
vector<int> centroid;
function<void (int, int)> dfs = [&](int u, int prev) {
sz[u] = 1;
bool is_centroid = true;
for (auto v : g[u]) if (v != prev && !dead[v]) {
dfs(v, u);
sz[u] += sz[v];
if (sz[v] > alive_cnt / 2) is_centroid = false;
}
if (alive_cnt - sz[u] > alive_cnt / 2) is_centroid = false;
if (is_centroid) centroid.push_back(u);
};
dfs(root, -1);
return centroid;
}
int main() {
init();
int n;
scanf("%d", &n);
vector<vector<int>> g(n);
for (int i = 0; i < n - 1; i ++) {
int a, b;
scanf("%d%d", &a, &b);
a --, b --;
g[a].push_back(b);
g[b].push_back(a);
}
vector<bool> dead(n);
auto get = Centroid(0, g, dead);
if (get.size() == 2) {
long long ans = fact[n / 2] * fact[n / 2] % MOD;
printf("%lld\n", ans);
return 0;
} else if (get.size() == 1) {
int centroid = get[0];
vector<int> sz(n);
function<void (int, int)> get_size = [&](int u, int prev) {
sz[u] = 1;
for (auto v : g[u]) if (v != prev) {
get_size(v, u);
sz[u] += sz[v];
}
};
get_size(centroid, -1);
vector<int> subtrees;
for (auto v : g[centroid]) subtrees.push_back(sz[v]);
int k = (int) subtrees.size();
vector<vector<long long>> dp(k + 1, vector<long long> (n + 1, 0));
dp[0][1] = 1;
for (int i = 0; i < k; i ++) {
int num = subtrees[i];
for (int j = 0; j <= n - num; j ++) {
for (int l = 0; l <= num; l ++) {
if (l & 1) {
(dp[i + 1][j + num - l] -= dp[i][j] * C(num, l) % MOD * fact[num] % MOD * invfact[num - l] % MOD) %= MOD;
} else {
(dp[i + 1][j + num - l] += dp[i][j] * C(num, l) % MOD * fact[num] % MOD * invfact[num - l] % MOD) %= MOD;
}
}
}
}
long long ans = 0;
for (int i = 0; i <= n; i ++) {
(ans += dp[k][i] * fact[i] % MOD) %= MOD;
}
ans = ((ans % MOD) + MOD) % MOD;
printf("%lld\n", ans);
} else {
printf("%d\n", 1 << 20);
}
return 0;
}
Submission Info
Submission Time |
|
Task |
F - Squirrel Migration |
User |
KokiYmgch |
Language |
C++14 (GCC 5.4.1) |
Score |
800 |
Code Size |
4275 Byte |
Status |
AC |
Exec Time |
1154 ms |
Memory |
313344 KB |
Compile Error
./Main.cpp: In function ‘int main()’:
./Main.cpp:59:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &n);
^
./Main.cpp:63:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
scanf("%d%d", &a, &b);
^
Judge Result
Set Name |
Sample |
All |
Score / Max Score |
0 / 0 |
800 / 800 |
Status |
|
|
Set Name |
Test Cases |
Sample |
0_00.txt, 0_01.txt, 0_02.txt, 0_03.txt |
All |
0_00.txt, 0_01.txt, 0_02.txt, 0_03.txt, 1_00.txt, 1_01.txt, 1_02.txt, 1_03.txt, 1_04.txt, 1_05.txt, 1_06.txt, 1_07.txt, 1_08.txt, 1_09.txt, 1_10.txt, 1_11.txt, 1_12.txt, 1_13.txt, 1_14.txt, 1_15.txt, 1_16.txt, 1_17.txt, 1_18.txt, 1_19.txt, 1_20.txt, 1_21.txt, 1_22.txt, 1_23.txt, 1_24.txt, 1_25.txt, 1_26.txt, 1_27.txt, 1_28.txt, 1_29.txt, 1_30.txt, 1_31.txt, 1_32.txt, 1_33.txt, 1_34.txt, 1_35.txt, 1_36.txt |
Case Name |
Status |
Exec Time |
Memory |
0_00.txt |
AC |
122 ms |
117376 KB |
0_01.txt |
AC |
122 ms |
117376 KB |
0_02.txt |
AC |
121 ms |
117376 KB |
0_03.txt |
AC |
123 ms |
117504 KB |
1_00.txt |
AC |
358 ms |
118144 KB |
1_01.txt |
AC |
127 ms |
118144 KB |
1_02.txt |
AC |
274 ms |
117760 KB |
1_03.txt |
AC |
417 ms |
117888 KB |
1_04.txt |
AC |
348 ms |
117888 KB |
1_05.txt |
AC |
424 ms |
117888 KB |
1_06.txt |
AC |
570 ms |
120576 KB |
1_07.txt |
AC |
570 ms |
120576 KB |
1_08.txt |
AC |
865 ms |
215552 KB |
1_09.txt |
AC |
1154 ms |
313344 KB |
1_10.txt |
AC |
753 ms |
215680 KB |
1_11.txt |
AC |
754 ms |
215680 KB |
1_12.txt |
AC |
575 ms |
121600 KB |
1_13.txt |
AC |
346 ms |
117888 KB |
1_14.txt |
AC |
404 ms |
117888 KB |
1_15.txt |
AC |
419 ms |
118016 KB |
1_16.txt |
AC |
460 ms |
118016 KB |
1_17.txt |
AC |
499 ms |
118272 KB |
1_18.txt |
AC |
536 ms |
118528 KB |
1_19.txt |
AC |
548 ms |
119424 KB |
1_20.txt |
AC |
557 ms |
120448 KB |
1_21.txt |
AC |
575 ms |
120576 KB |
1_22.txt |
AC |
576 ms |
122624 KB |
1_23.txt |
AC |
595 ms |
127488 KB |
1_24.txt |
AC |
622 ms |
137216 KB |
1_25.txt |
AC |
691 ms |
156800 KB |
1_26.txt |
AC |
699 ms |
165632 KB |
1_27.txt |
AC |
761 ms |
182656 KB |
1_28.txt |
AC |
859 ms |
215168 KB |
1_29.txt |
AC |
122 ms |
117376 KB |
1_30.txt |
AC |
122 ms |
117376 KB |
1_31.txt |
AC |
123 ms |
117760 KB |
1_32.txt |
AC |
128 ms |
117760 KB |
1_33.txt |
AC |
123 ms |
117760 KB |
1_34.txt |
AC |
123 ms |
117760 KB |
1_35.txt |
AC |
123 ms |
117760 KB |
1_36.txt |
AC |
129 ms |
117760 KB |