QOJ.ac
QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#94970 | #6137. Sub-cycle Graph | ysghwzp# | AC ✓ | 121ms | 4512kb | C++20 | 1.3kb | 2023-04-08 15:13:15 | 2023-04-08 15:13:19 |
Judging History
answer
#include <bits/stdc++.h>
using i64 = long long;
constexpr int N = 1E5;
constexpr int P = 1E9 + 7;
int fac[N + 1], invfac[N + 1], inv[N + 1];
int power(int a, int b) {
int res = 1;
for (; b; b /= 2, a = 1LL * a * a % P) {
if (b % 2) {
res = 1LL * res * a % P;
}
}
return res;
}
int binom(int n, int m) {
if (n < m || m < 0) {
return 0;
}
return 1LL * fac[n] * invfac[m] % P * invfac[n - m] % P;
}
void solve() {
int n;
i64 m;
std::cin >> n >> m;
if (n < m) {
std::cout << 0 << "\n";
return;
}
if (n == m) {
std::cout << 1LL * fac[n - 1] * (P + 1) / 2 % P << "\n";
return;
}
m = n - m;
int ans = 0;
for (int i = 0; i < m; i++) {
ans = (ans + 1LL * binom(m, i) * binom(n - m + m - i - 1, m - i - 1)) % P;
}
if (m == n) {
ans = (ans + 1) % P;
}
ans = 1LL * ans * fac[n] % P * invfac[m] % P * power((P + 1) / 2, m) % P;
std::cout << ans << "\n";
}
int main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
fac[0] = 1;
for (int i = 1; i <= N; i++) {
fac[i] = 1LL * fac[i - 1] * i % P;
}
invfac[N] = power(fac[N], P - 2);
for (int i = N; i; i--) {
invfac[i - 1] = 1LL * invfac[i] * i % P;
inv[i] = 1LL * invfac[i] * fac[i - 1] % P;
}
int T;
std::cin >> T;
while (T--) {
solve();
}
return 0;
}
Details
Tip: Click on the bar to expand more detailed information
Test #1:
score: 100
Accepted
time: 3ms
memory: 4512kb
input:
3 4 2 4 3 5 3
output:
15 12 90
result:
ok 3 number(s): "15 12 90"
Test #2:
score: 0
Accepted
time: 121ms
memory: 4488kb
input:
17446 3 0 3 1 3 2 3 3 4 0 4 1 4 2 4 3 4 4 5 0 5 1 5 2 5 3 5 4 5 5 6 0 6 1 6 2 6 3 6 4 6 5 6 6 7 0 7 1 7 2 7 3 7 4 7 5 7 6 7 7 8 0 8 1 8 2 8 3 8 4 8 5 8 6 8 7 8 8 9 0 9 1 9 2 9 3 9 4 9 5 9 6 9 7 9 8 9 9 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 11 0 11 1 11 2 11 3 11 4 11 5 11 6 11 7 11...
output:
1 3 3 1 1 6 15 12 3 1 10 45 90 60 12 1 15 105 375 630 360 60 1 21 210 1155 3465 5040 2520 360 1 28 378 2940 13545 35280 45360 20160 2520 1 36 630 6552 42525 170100 393120 453600 181440 20160 1 45 990 13230 114345 643545 2286900 4762800 4989600 1814400 181440 1 55 1485 24750 273735 2047815 10239075 3...
result:
ok 17446 numbers