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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#155697 | #6410. Classical DP Problem | Forever_Young# | WA | 20ms | 105480kb | C++14 | 3.9kb | 2023-09-02 01:08:16 | 2023-09-02 01:08:17 |
Judging History
answer
#include<bits/stdc++.h>
#define rep(i,s,t) for(int i = s;i <= t;i ++)
using namespace std;
int n,a[5050],r,dp[5050][5050],res,fac[5050],ifac[5050],g[5050][5050],nt[10100],ant[10100];
const int mod=998244353;
const int NN=5050;
typedef long long ll;
int qpow(int x,int y){
int res=1;
while (y){
if (y&1) res=1ll*res*x%mod;
x=1ll*x*x%mod;
y/=2;
}
return res;
}
//NTT
namespace NTT{
const int g=3;
int x[NN<<2],y[NN<<2],wn[NN<<2];
void init()
{
rep(i,0,20)wn[i]=qpow(g,(mod-1)/(1<<i));
}
void brc(int *F,int len)
{
int j=len/2;
rep(i,1,len-2){
if(i<j)swap(F[i],F[j]);
int k=len/2;
while(j>=k) j-=k,k>>=1;
if(j<k)j+=k;
}
}
void NTT(int *F,int len,int t)
{
int id=0; brc(F,len);
for(int h=2;h<=len;h<<=1)
{
id++;
for(int j=0;j<len;j+=h)
{
int E=1;
for(int k=j;k<j+h/2;k++)
{
int u=F[k],v=(ll)E*F[k+h/2]%mod;
F[k]=(u+v)%mod,F[k+h/2]=((u-v)%mod+mod)%mod;
E=(ll)E*wn[id]%mod;
}
}
}
if(t==-1)
{
rep(i,1,len/2-1)swap(F[i],F[len-i]);
ll inv=qpow(len,mod-2);
rep(i,0,len-1)F[i]=(ll)F[i]%mod*inv%mod;
}
}
void multiply(int *a,int len1,int *b,int len2)
{
int len=1;
while(len<len1+len2)len<<=1;
rep(i,len1,len-1)a[i]=0;
rep(i,len2,len-1)b[i]=0;
NTT(a,len,1); NTT(b,len,1);
rep(i,0,len-1)a[i]=(ll)a[i]*b[i]%mod;
NTT(a,len,-1);
}
void mpow(int *a,int len1,int *b,int len2,int y)
{
int len=1;
while(len<len1+len2)len<<=1;
rep(i,len1,len-1)a[i]=0;
rep(i,len2,len-1)b[i]=0;
NTT(a,len,1); NTT(b,len,1);
rep(i,0,len-1)a[i]=(ll)a[i]*qpow(b[i],y)%mod;
NTT(a,len,-1);
}
}
int c(int x,int y){//x>=y
if (x<y) return 0;
return 1ll*fac[x]*ifac[y]%mod*ifac[x-y]%mod;
}
int main(){
//freopen("D.in","r",stdin);
NTT::init();
scanf("%d",&n);
for (int i=1;i<=n;i++)
scanf("%d",&a[i]);
for (int i=n;i;i--){
if (r>=a[i]) break;
r++;
}
dp[n][a[n-r]]=1;
for (int i=n;i>n-r;i--)
for (int j=0;j<=a[n-r];j++){
//printf("%d %d %d\n",i,j,dp[0][i][j]);
dp[i-1][j]=(dp[i-1][j]+1ll*dp[i][j]*(a[i]-j))%mod;
if (j)
dp[i-1][j-1]=(dp[i-1][j-1]+1ll*dp[i][j]*j)%mod;
}
res=dp[n-r][0];
memset(dp,0,sizeof(dp));
//printf("%d\n",res);
dp[n][a[n-r+1]]=1;
for (int i=n;i>n-r;i--)
for (int j=0;j<=a[n-r+1];j++){
//printf("%d %d %d\n",i,j,dp[0][i][j]);
dp[i-1][j]=(dp[i-1][j]+1ll*dp[i][j]*(a[i]-j))%mod;
if (j)
dp[i-1][j-1]=(dp[i-1][j-1]+1ll*dp[i][j]*j)%mod;
}
res=(res-dp[n-r][0]+mod)%mod;
memset(dp,0,sizeof(dp));
//printf("%d\n",res);
if (r==a[n-r+1]){
fac[0]=1;
for (int i=1;i<=n;i++) fac[i]=1ll*fac[i-1]*i%mod;
ifac[n]=qpow(fac[n],mod-2);
for (int i=n;i;i--) ifac[i-1]=1ll*ifac[i]*i%mod;
g[1][0]=1;
int i=1;
while (i<=n){
int z=min(a[i],r);
for (int j=0;j<=z;j++){
nt[j]=1ll*g[i][j]*fac[z-j]%mod;
ant[j]=ifac[j];
}
int tmp=i;
while (a[tmp]==a[i]) tmp++;
if (a[i]>r){
ant[0]=0;
tmp=n+1;
}
NTT::mpow(nt,z+1,ant,z+1,tmp-i);
for (int j=0;j<=z;j++) g[tmp][j]=1ll*nt[j]*ifac[z-j]%mod;
i=tmp;
//for (int j=0;j<=z;j++) printf("%d %d %d\n",i,j,g[i][j]);
/*
if (a[i]<=r){
for (int j=0;j<=r;j++) g[i+1][j]=(g[i+1][j]+g[i][j])%mod;
}
for (int j=0;j<r;j++){
if (g[i][j]==0) continue;
for (int k=j+1;k<=r&&k<=a[i];k++){
g[i+1][k]=(g[i+1][k]+1ll*g[i][j]*c(min(a[i],r)-j,k-j))%mod;
}
}
*/
}
//printf("%d\n",g[n+1][r]);
res=(res+g[n+1][r])%mod;
}
printf("%d %d\n",r,res);
}
Details
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Test #1:
score: 100
Accepted
time: 11ms
memory: 105356kb
input:
3 1 2 3
output:
2 6
result:
ok 2 number(s): "2 6"
Test #2:
score: 0
Accepted
time: 16ms
memory: 104368kb
input:
1 1
output:
1 1
result:
ok 2 number(s): "1 1"
Test #3:
score: 0
Accepted
time: 8ms
memory: 105308kb
input:
2 1 1
output:
1 2
result:
ok 2 number(s): "1 2"
Test #4:
score: 0
Accepted
time: 20ms
memory: 104772kb
input:
2 2 2
output:
2 6
result:
ok 2 number(s): "2 6"
Test #5:
score: 0
Accepted
time: 18ms
memory: 104820kb
input:
3 1 1 1
output:
1 3
result:
ok 2 number(s): "1 3"
Test #6:
score: 0
Accepted
time: 12ms
memory: 105476kb
input:
3 2 2 2
output:
2 9
result:
ok 2 number(s): "2 9"
Test #7:
score: 0
Accepted
time: 12ms
memory: 104528kb
input:
3 3 3 3
output:
3 48
result:
ok 2 number(s): "3 48"
Test #8:
score: 0
Accepted
time: 9ms
memory: 105480kb
input:
5 1 1 3 3 4
output:
3 47
result:
ok 2 number(s): "3 47"
Test #9:
score: -100
Wrong Answer
time: 12ms
memory: 105368kb
input:
10 2 4 5 5 5 5 6 8 8 10
output:
5 267546521
result:
wrong answer 2nd numbers differ - expected: '864', found: '267546521'