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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 |
---|---|---|---|---|---|---|---|---|---|
#94466 | #6137. Sub-cycle Graph | xuzhihaodedie | AC ✓ | 345ms | 8772kb | C++14 | 1.4kb | 2023-04-06 10:51:22 | 2023-04-06 10:51:26 |
Judging History
answer
// Problem: E. Living Sequence
// Contest: Codeforces - Codeforces Round 863 (Div. 3)
// URL: https://codeforces.com/contest/1811/problem/E
// Memory Limit: 256 MB
// Time Limit: 1000 ms
//
// Powered by CP Editor (https://cpeditor.org)
#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod=1e9+7;
const int N=1e5+10;
int fact[2*N],infact[2*N];
int pw[2*N];
int f[2*N];
int qpow(int a,int b) {
if(b==0) return 1;
if(b&1) return a*qpow(a,b-1)%mod;
else {
int mul=qpow(a,b/2)%mod;
return mul*mul%mod;
}
}
void init() {
fact[0]=infact[0]=pw[0]=f[0]=1;
for(int i=1;i<2*N;i++) {
fact[i]=fact[i-1]*i%mod;
infact[i]=qpow(fact[i],mod-2)%mod;
pw[i]=pw[i-1]*2%mod;
}
for(int i=1;i<N;i++) {
f[i]=f[i-1]*(2*i-1)%mod;
}
}
int c(int n,int m) {
if(n<m) return 0;
if(n<0||m<0) return 0;
return fact[n]*infact[n-m]%mod*infact[m]%mod;
}
void solve() {
int n,m;
cin>>n>>m;
if(m>n) {
cout<<0<<endl;
return ;
}
if(m==0) {
cout<<1<<endl;
return ;
}
if(m==n) {
if(n<=2) {
cout<<0<<endl;
} else {
cout<<fact[n-1]*qpow(2,mod-2)%mod<<endl;
}
return ;
}
int ans=0;
for(int t=0;t<=n-m;t++) {
int res=c(n,t)*c(n-t,2*(n-m-t))%mod*c(m-1,n-m-t-1)%mod;
int ret=f[n-m-t];
ans=(ans+ret*res%mod*fact[max(0ll,2*m+t-n)]%mod)%mod;
}
cout<<ans<<endl;
}
signed main() {
int T=1;
init();
cin>>T;
while(T--) {
solve();
}
}
详细
Test #1:
score: 100
Accepted
time: 58ms
memory: 8756kb
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: 345ms
memory: 8772kb
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