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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#818924 | #6137. Sub-cycle Graph | fairyqq28 | AC ✓ | 355ms | 472608kb | C++14 | 1.1kb | 2024-12-18 10:53:35 | 2024-12-18 10:53:36 |
Judging History
answer
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#define rep(i, a, b) for(int i = (a); i <= (b); i++)
#define per(i, a, b) for(int i = (a); i >= (b); i--)
using namespace std;
typedef long long ll;
const int N = 30000010;
const ll mod = 1000000007, inv2 = (mod+1)>>1;
ll qpow(ll x, ll y = mod - 2){
ll ret = 1;
for(; y; y >>= 1, (x *= x) %= mod) if(y & 1) (ret *= x) %= mod;
return ret;
}
ll fac[N], ifac[N];
ll C(ll x, ll y){
if(x < y || y < 0) return 0;
return fac[x] * ifac[x-y] % mod * ifac[y] % mod;
}
int n;
ll m, ans;
void solve(){
scanf("%d%lld", &n, &m);
if(!m) {puts("1"); return;}
if(n < m) {puts("0"); return;}
if(n == m) {printf("%lld\n", fac[n-1] * inv2 % mod); return;}
ll pw = 1;
ans = 0;
rep(i, 1, n-m){
(pw *= inv2) %= mod;
(ans += C(n-m, i) * C(m-1, i-1) % mod * pw) %= mod;
}
(ans *= fac[n] * ifac[n-m] % mod) %= mod;
printf("%lld\n", ans);
}
int main(){
fac[0] = 1; rep(i, 1, N-5) fac[i] = fac[i-1] * i % mod;
ifac[N-5] = qpow(fac[N-5]);
per(i, N-6, 0) ifac[i] = ifac[i+1] * (i+1) % mod;
int T; scanf("%d", &T); while(T--) solve();
return 0;
}
Details
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Test #1:
score: 100
Accepted
time: 283ms
memory: 472604kb
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: 355ms
memory: 472608kb
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