Bomb HDU - 3555 数位dp

Code:

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<string>
#include<iostream>
using namespace std;
#define ll long long
#define N 20
ll f[N][4], str;
int arr[N],n;
void get_table(){
    f[0][0]=1;
    for(int i=1;i<N;++i){
        f[i][0]=f[i-1][0]*10-f[i-1][1];
        f[i][1]=f[i-1][0];
        f[i][2]=f[i-1][2]*10+f[i-1][1];
    }
}
ll solve(){
    ll ans=0;
    bool flag=false;
    for(int i=n;i>=1;--i){
        ans+=f[i-1][2]*arr[i];
        if(flag) ans+=f[i-1][0]*arr[i];
        if(arr[i]>4 && !flag) ans+=f[i-1][1];
        if(arr[i+1]==4&&arr[i]==9) flag=true;
    }
    return ans;
}
int main(){
    //freopen("input.in","r",stdin);
    get_table();
    int T;
    scanf("%d",&T);
    while(T--){
        scanf("%I64d",&str);
        memset(arr,0,sizeof(arr));
        str++,n=0;
        while(str){
            arr[++n]=str%10;
            str/=10;
        }
        printf("%I64d\n",solve());
    }
    return 0;
}