hdu3555（数位dp）

#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <queue>
#include <cstdlib>
#include <stack>
#include <vector>
#include <set>
#include <map>
#define LL long long
#define mod 10007
#define inf 0x3f3f3f3f
#define N 100010
#define FILL(a,b) (memset(a,b,sizeof(a)))
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
using namespace std;
LL dp[22][3];
int dig[22];
LL dfs(int pos,int pre,bool flag,bool limit)
{
    if(pos==0)return flag;
    if(!limit&&flag&&~dp[pos][2])return dp[pos][2];
    if(!limit&&!flag&&pre==4&&~dp[pos][1])return dp[pos][1];
    if(!limit&&!flag&&pre!=4&&~dp[pos][0])return dp[pos][0];
    int len=limit?dig[pos]:9;
    LL ans=0;
    for(int i=0;i<=len;i++)
    {
        if(pre==4&&i==9)ans+=dfs(pos-1,i,flag||1,limit&&i==len);
        else ans+=dfs(pos-1,i,flag||0,limit&&i==len);
    }
    if(!limit)//分情况记录状态
    {
        if(flag)dp[pos][2]=ans;
        else if(pre==4)dp[pos][1]=ans;
        else dp[pos][0]=ans;
    }
    return ans;
}
LL solve(LL x)
{
    int len=0;
    while(x)
    {
        dig[++len]=x%10;
        x/=10;
    }
    LL ans=dfs(len,0,0,1);
    return ans;
}
int main()
{
    LL n,T;
    scanf("%I64d",&T);
    while(T--)
    {
        scanf("%I64d",&n);
        memset(dp,-1,sizeof(dp));
        printf("%I64d\n",solve(n));
    }
}