| # |
Submission time |
Handle |
Problem |
Language |
Result |
Execution time |
Memory |
| 19424 |
2016-02-24T12:05:08 Z |
Qwaz |
Ω (kriii4_P3) |
C++14 |
|
0 ms |
1084 KB |
#include <cstdio>
typedef long long ll;
const int MOD = 1000000007, MAX = 110;;
ll modpow(ll a, ll x) {
ll ret = 1;
a = a % MOD;
while (x) {
if (x & 1) ret = ret * a % MOD;
a = a * a % MOD;
x >>= 1;
}
return ret;
}
int p, q, n, k;
ll coeff[MAX], constant[MAX], val[MAX];
int main() {
scanf("%d%d%d%d", &p, &q, &n, &k);
if (k == 0) puts("0");
else if (k == n) puts("1");
else {
ll x = q * modpow(p, MOD-2) % MOD;
ll y = 1 - x;
if (y < 0) y += MOD;
coeff[n] = 0;
constant[n] = 1;
for (int i = n-1; i > 0; i--) {
ll div = 1 - y * coeff[i+1];
div %= MOD;
if (div < 0) div += MOD;
div = modpow(div, MOD-2);
coeff[i] = x * div % MOD;
constant[i] = (y * constant[i+1] % MOD) * div % MOD;
}
val[0] = 0;
val[1] = constant[1];
for (int i = 2; i < n; i++) {
val[i] = (coeff[i] * val[i-1] + constant[i]) % MOD;
}
printf("%lld\n", val[k]);
}
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 2 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 3 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 4 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 5 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 6 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 7 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 8 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 9 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 10 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 11 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 12 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 13 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 14 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 15 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 16 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 17 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 18 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 19 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 20 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 21 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 22 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 23 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 24 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 25 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 26 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 27 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 28 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 29 |
Correct |
0 ms |
1084 KB |
Output is correct |
| 30 |
Correct |
0 ms |
1084 KB |
Output is correct |
