#include <stdio.h>
#define N 3000
#define M 3000
#define MD 1000000007
int vv[N + 1], ff[N + 1], gg[N + 1], dp[N + 1][M + 1];
void init() {
int i, j;
ff[0] = gg[0] = 1;
for (i = 1; i <= N; i++) {
vv[i] = i == 1 ? 1 : (long long) vv[i - MD % i] * (MD / i + 1) % MD;
ff[i] = (long long) ff[i - 1] * i % MD;
gg[i] = (long long) gg[i - 1] * vv[i] % MD;
}
for (i = 0; i <= N; i++)
for (j = 0; j <= M; j++)
if (i == 0)
dp[i][j] = j == 0 ? 1 : 0;
else
dp[i][j] = (dp[i - 1][j] + (j == 0 ? 0 : (long long) dp[i - 1][j - 1] * j * 2) + (j < 2 ? 0 : (long long) dp[i - 1][j - 2] * j * (j - 1) / 2)) % MD;
}
int choose(int n, int k) {
return (long long) ff[n] * gg[k] % MD * gg[n - k] % MD;
}
int main() {
int n, m, i, j, ans;
init();
scanf("%d%d", &n, &m);
ans = 0;
for (i = 0; i <= n; i++)
for (j = 0; j <= m; j++)
ans = (ans + (long long) dp[i][j] * dp[m - j][n - i] % MD * choose(n, i) % MD * choose(m, j) % MD) % MD;
ans = (ans - 1 + MD) % MD;
printf("%d\n", ans);
return 0;
}
Compilation message
tents.c: In function 'main':
tents.c:34:2: warning: ignoring return value of 'scanf' declared with attribute 'warn_unused_result' [-Wunused-result]
34 | scanf("%d%d", &n, &m);
| ^~~~~~~~~~~~~~~~~~~~~
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
41 ms |
35544 KB |
Output is correct |
2 |
Correct |
42 ms |
35548 KB |
Output is correct |
3 |
Correct |
42 ms |
35512 KB |
Output is correct |
4 |
Correct |
43 ms |
35552 KB |
Output is correct |
5 |
Correct |
43 ms |
35528 KB |
Output is correct |
6 |
Correct |
42 ms |
35532 KB |
Output is correct |
7 |
Correct |
43 ms |
35520 KB |
Output is correct |
8 |
Correct |
43 ms |
35540 KB |
Output is correct |
9 |
Correct |
45 ms |
35512 KB |
Output is correct |
10 |
Correct |
43 ms |
35480 KB |
Output is correct |
11 |
Correct |
47 ms |
35484 KB |
Output is correct |
12 |
Correct |
44 ms |
35520 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
41 ms |
35544 KB |
Output is correct |
2 |
Correct |
42 ms |
35548 KB |
Output is correct |
3 |
Correct |
42 ms |
35512 KB |
Output is correct |
4 |
Correct |
43 ms |
35552 KB |
Output is correct |
5 |
Correct |
43 ms |
35528 KB |
Output is correct |
6 |
Correct |
42 ms |
35532 KB |
Output is correct |
7 |
Correct |
43 ms |
35520 KB |
Output is correct |
8 |
Correct |
43 ms |
35540 KB |
Output is correct |
9 |
Correct |
45 ms |
35512 KB |
Output is correct |
10 |
Correct |
43 ms |
35480 KB |
Output is correct |
11 |
Correct |
47 ms |
35484 KB |
Output is correct |
12 |
Correct |
44 ms |
35520 KB |
Output is correct |
13 |
Correct |
43 ms |
35540 KB |
Output is correct |
14 |
Correct |
43 ms |
35524 KB |
Output is correct |
15 |
Correct |
177 ms |
35548 KB |
Output is correct |
16 |
Correct |
50 ms |
35536 KB |
Output is correct |
17 |
Correct |
72 ms |
35480 KB |
Output is correct |
18 |
Correct |
69 ms |
35536 KB |
Output is correct |
19 |
Correct |
193 ms |
35540 KB |
Output is correct |
20 |
Correct |
164 ms |
35456 KB |
Output is correct |
21 |
Correct |
120 ms |
35548 KB |
Output is correct |
22 |
Correct |
116 ms |
35568 KB |
Output is correct |
23 |
Correct |
67 ms |
35476 KB |
Output is correct |
24 |
Correct |
255 ms |
35548 KB |
Output is correct |
25 |
Correct |
201 ms |
35552 KB |
Output is correct |
26 |
Correct |
223 ms |
35472 KB |
Output is correct |
27 |
Correct |
244 ms |
35508 KB |
Output is correct |