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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#65756 | #4843. Infectious Disease | lqx123123 | WA | 6ms | 11848kb | C++14 | 1.5kb | 2022-12-03 16:33:07 | 2022-12-03 16:33:10 |
Judging History
answer
#include<bits/stdc++.h>
using namespace std;
const int mod=1e9+7;
const int N=14e6+6;
int n;
int jie[N],inv[N],top,pow3[20];
int dp[2][N];
bool v[N];
vector<int>id;
inline void add(int &x,int y){
x+=y-(x+y>=mod?mod:0);
}
int ksm(int a,int b){
int ans=1;
while(b){
if(b&1)ans=(1ll*ans*a)%mod;
a=1ll*a*a%mod;
b>>=1;
}
return ans;
}
void init(int lim){
jie[0]=1;
for(int i=1;i<=lim;i++)jie[i]=1ll*jie[i-1]*i%mod;
inv[lim]=ksm(jie[lim],mod-2);
for(int i=lim;i>=1;i--)inv[i-1]=1ll*inv[i]*i%mod;
pow3[0]=1;
while(pow3[top]<n)pow3[++top]=pow3[top-1]*3;
}
int C(int n,int m){
return 1ll*jie[n]*inv[m]%mod*inv[n-m]%mod;
}
int invC(int n,int m){
return 1ll*inv[n]*jie[m]%mod*jie[n-m]%mod;
}
int main(){
scanf("%d",&n);
init(n);
int ans=0;
dp[0][1]=1;
for(int i=1;i<=top;i++){
int p=i&1,q=p^1;
int lim=min(n-pow3[i-1],2*pow3[i-1]);
int inv_num=invC(n-pow3[i-1],lim);
for(int j=1;j<=(1<<i-1)&&j<=n&&j+pow3[i-1]<=n;j++){
int infected=min(n-pow3[i-1]-j,j);
for(int k=0;k<=j+infected&&k<=lim;k++){
int temp=1ll*C(j+infected,k)*C(n-pow3[i-1]-j-infected,lim-k)%mod;
temp=(1ll*temp*inv_num)%mod;
temp=(1ll*temp*dp[q][j])%mod;
if(!v[j+infected-k]){
dp[p][j+infected-k]=0;
v[j+infected-k]=1;
id.push_back(j+infected-k);
}
add(dp[p][j+infected-k],temp);
}
}
for(auto x:id)v[x]=0;
id.clear();
add(ans,1ll*dp[p][0]*i%mod);
//printf("%d:%d\n",i,3ll*dp[p][0]%mod);
}
printf("%d\n",ans);
//printf("%d\n",5ll*ksm(3,mod-2)%mod);
}
Details
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Test #1:
score: 100
Accepted
time: 6ms
memory: 11816kb
input:
2
output:
1
result:
ok 1 number(s): "1"
Test #2:
score: -100
Wrong Answer
time: 3ms
memory: 11848kb
input:
114
output:
106604856
result:
wrong answer 1st numbers differ - expected: '505208013', found: '106604856'