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QOJ
ID | 题目 | 提交者 | 结果 | 用时 | 内存 | 语言 | 文件大小 | 提交时间 | 测评时间 |
---|---|---|---|---|---|---|---|---|---|
#93971 | #6137. Sub-cycle Graph | ksunhokim | AC ✓ | 129ms | 5140kb | C++20 | 1.3kb | 2023-04-04 12:03:53 | 2023-04-04 12:03:55 |
Judging History
answer
#include <bits/stdc++.h>
#define MAXN ((int) 1e5)
#define MOD ((int) 1e9 + 7)
using namespace std;
int n;
long long ans, m;
long long fac[MAXN + 10], ifac[MAXN + 10];
long long C(int a, int b) {
return fac[a] * ifac[b] % MOD * ifac[a - b] % MOD;
}
void solve() {
scanf("%d%lld", &n, &m);
if (m == 0) printf("1\n");
else if (m > n) printf("0\n");
else if (m == n) printf("%lld\n", fac[n - 1] * ifac[2] % MOD);
else {
ans = 0;
// f is the \prod in the tutorial
long long f = 1;
for (int i = 1; i <= n - m; i++) {
if (m + i < i * 2) continue;
long long t = C(m + i, i * 2) * f % MOD;
f = f * (i * 2 + 1) % MOD;
t = t * fac[m - i] % MOD;
t = t * C(m - 1, i - 1) % MOD;
ans = (ans + C(n, n - m - i) * t) % MOD;
}
printf("%lld\n", ans);
}
}
int main() {
fac[0] = 1;
for (int i = 1; i <= MAXN; i++) fac[i] = fac[i - 1] * i % MOD;
ifac[0] = ifac[1] = 1;
for (int i = 2; i <= MAXN; i++) ifac[i] = (MOD - MOD / i) * ifac[MOD % i] % MOD;
for (int i = 2; i <= MAXN; i++) ifac[i] = ifac[i - 1] * ifac[i] % MOD;
int tcase; scanf("%d", &tcase);
while (tcase--) solve();
return 0;
}
詳細信息
Test #1:
score: 100
Accepted
time: 2ms
memory: 5140kb
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: 129ms
memory: 5116kb
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