HDU 3555 Bomb （数位DP）

#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int mxn = 25 ;
ll n,m,k,t,dp[mxn][3],lim[mxn];
ll dfs(int pos , int state , int limit)
{
    if(!pos) return 1;
    if(!limit && dp[pos][state]!=-1) return dp[pos][state];
    int up = limit ? lim[pos] : 9 ;
    ll ans = 0 ;
    for(int i=0;i<=up;i++)
    {
        if( ( state && i==9)) continue ;
        ans += dfs(pos-1, i==4 , limit && i==lim[pos] ) ;
    }
    if(!limit) dp[pos][state] = ans;
    return ans;
}
ll cal(ll x)
{
    int len = 0;
    memset(lim,0,sizeof(lim));
    memset(dp,-1,sizeof(dp));
    while(x) lim[++len] = x%10 , x/=10 ;
    return dfs(len,false,true);
}
int main()
{
    cin>>t;
    while(t--)
    {
        cin>>n;
        cout<<n-cal(n)+1<<endl;
    }
    return 0;
}