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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#808964 | #6137. Sub-cycle Graph | lichenghan | AC ✓ | 85ms | 6184kb | C++17 | 1.1kb | 2024-12-11 10:02:16 | 2024-12-11 10:02:17 |
Judging History
answer
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int L=2e5+10;
const int mod=1e9+7;
inline constexpr int qpow(ll x,ll y=mod-2){
ll r=1;
for(x%=mod;y;y>>=1,x=x*x%mod) if(y&1) r=r*x%mod;
return r;
}
int fac[L],ifac[L];
int p[L];
void init_fac(){
fac[0]=ifac[0]=1;
for(int i=1;i<L;i++) fac[i]=(ll)fac[i-1]*i%mod;
ifac[L-1]=qpow(fac[L-1]);
for(int i=L-2;i>=1;i--) ifac[i]=(ll)ifac[i+1]*(i+1)%mod;
p[0]=1; p[1]=mod-qpow(2);
for(int i=2;i<L;i++) p[i]=(ll)p[i-1]*p[1]%mod;
}
int binom(int u,int d){
if(d<0||d>u) return 0;
return (ll)fac[u]*ifac[d]%mod*ifac[u-d]%mod;
}
void solve(){
int n,m;
scanf("%d%d",&n,&m);
if(m>n) puts("0");
else if(m==n) printf("%lld\n",(ll)fac[n-1]*qpow(2)%mod);
else {
int ans=0;
int c=n-m;
for(int i=0;i<=c;i++) {
ans=(ans+(ll)p[i]*binom(c,i)%mod*binom(c-1+n-c-i,c-1))%mod;
// printf("%d: %d\n",i,(ll)qpow(mod-qpow(2),i)*binom(c,i)%mod*binom(c-1+n-c-i,c-1)%mod);
}
ans=(ll)ans*fac[n]%mod*ifac[c]%mod;
printf("%d\n",ans);
}
}
signed main(){
init_fac();
signed tc;
scanf("%d",&tc);
while(tc--){
solve();
}
}
Details
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Test #1:
score: 100
Accepted
time: 0ms
memory: 6108kb
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: 85ms
memory: 6184kb
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