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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
#142804#6137. Sub-cycle GraphNyansAC ✓66ms3600kbC++141.1kb2023-08-19 22:50:372023-08-19 22:50:38

Judging History

你现在查看的是最新测评结果

  • [2023-08-19 22:50:38]
  • 评测
  • 测评结果:AC
  • 用时:66ms
  • 内存:3600kb
  • [2023-08-19 22:50:37]
  • 提交

answer

#include <cstdio>
#define mod 1000000007
int qpow(int a, int b) {
	int ans = 1;
	for (; b; b >>= 1, a = a * 1ll * a % mod)
		if (b & 1) ans = ans * 1ll * a % mod;
	return ans;
}
int T, n;
long long m;
int fac[200010], ifac[200010], ffac[200010];
main() {
	n = 2e5, fac[0] = ffac[0] = 1;
	for (int i = 1; i <= n; ++i) fac[i] = fac[i - 1] * 1ll * i % mod;
	ifac[n] = qpow(fac[n], mod - 2);
	for (int i = n; i; --i) ifac[i - 1] = ifac[i] * 1ll * i % mod;
	for (int i = 1; i <= n / 2; ++i) ffac[i] = ffac[i - 1] * (2ll * i - 1) % mod;
	for (int i = 1; i <= n / 2; ++i) ffac[i] = ffac[i] * 1ll * ifac[i * 2] % mod * ifac[i - 1] % mod;
	for (scanf("%d", &T); T--; ) {
		scanf("%d%lld", &n, &m);
		if (m > n) { puts("0"); continue; }
		if (m == 0) { puts("1"); continue; }
		if (n == m) {
			printf("%d\n", (fac[n - 1] + (fac[n - 1] % 2? mod: 0)) / 2);
			continue;
		}
		int ans = 0;
		for (int i = 1; i <= n - m; ++i) 
			ans = (ans + 1ll * ifac[n - m - i] * ffac[i] % mod * ifac[m - i]) % mod;
		printf("%d\n", ans * 1ll * fac[n] % mod * fac[m - 1] % mod);
	}
}

详细

Test #1:

score: 100
Accepted
time: 3ms
memory: 3576kb

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: 66ms
memory: 3600kb

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