HDU 6093 Rikka with Number

#include<bits/stdc++.h>using namespace std;const int MAXN=5050;const long long mod=998244353;char ch[MAXN];double L[MAXN];int I[MAXN],A[MAXN],B[MAXN],C[MAXN],pd[MAXN];int x[MAXN],y[MAXN],lenx,leny;int len,le; void change(int len,int m){int x,pre,i;le=0;memcpy(B,A,sizeof(A));while(len){x=0;for(i=len;i;i--){pre=x;x=(x*10+B[i])%m;B[i]=(pre*10+B[i])/m;}C[++le]=x;while(len&&B[len]==0)len--;}}int calc(int m){change(len,m);if(le>m)return (I[m]-I[m-1]+mod)%mod;if(le<m)return 0;int i,j,ans;for(i=0;i<m;i++)pd[i]=0;ans=0;for(i=1;i<C[le];i++)ans=(ans+I[le-1])%mod;pd[C[le]]=1;for(i=le-1;i>0;i--){for(j=0;j<C[i];j++){if(pd[j]==0)ans=(ans+I[i-1])%mod;}if(pd[C[i]])break;pd[C[i]]=1;if(i==1)ans=(ans+1)%mod;} return ans;}int calc(){if(len==0)return 0;int ans,where,i;ans=0;where=2;while(L[where]<=len-1)where++;if(where<=15){for(i=2;i<=15;i++)ans=(ans+calc(i))%mod;return ans;}for(i=2;i<=where-2;i++)ans=((ans+I[i]-I[i-1])%mod+mod)%mod;ans=(ans+calc(where-1)+calc(where))%mod;return ans;}int main(){int i,T,lenx,ans;len=1;while(L[len]<MAXN){len++;L[len]=log(len)/log(10)*(len-1);}I[0]=1;for(i=1;i<MAXN;i++)I[i]=I[i-1]*1ll*i%mod;scanf("%d",&T);while(T--){scanf("%s",ch+1);len=strlen(ch+1);for(i=1;i<=len;i++)A[i]=ch[len-i+1]-'0';lenx=len;for(i=1;i<=len;i++)x[i]=A[i];A[1]--;for(i=1;i<=len;i++){if(A[i]<0){A[i+1]--;A[i]+=10;}}while(len&&A[len]==0)len--;ans=calc();scanf("%s",ch+1);len=strlen(ch+1);for(i=1;i<=len;i++)A[i]=ch[len-i+1]-'0';leny=len;for(i=1;i<=len;i++)y[i]=A[i];ans=(calc()-ans+mod)%mod;printf("%d\n",ans);}}