FOJ1682

题意：给你n，让你求1到n中有多少个数字，它的每位不能为3和6.

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<iostream>
#include<algorithm>
using namespace std;

#define ll long long

ll h[30];
char s[30];
int len,num[30];
ll dfs(int k,int jg){
    if(k==-1)return 1;
    if(h[k]!=-1&&!jg)return h[k];
    int tmp=jg?num[k]:9;
    ll tans=0;
    for(int i=0;i<=tmp;i++){
        if(i==3||i==6)continue;
        tans+=dfs(k-1,jg&&(i==tmp));
    }
    if(!jg)h[k]=tans;
    return tans;
}
int main(){
    int i,j;
    memset(h,-1,sizeof(h));
    while(scanf("%s",s)!=EOF){
        int len=strlen(s);
        for(i=len-1,j=0;i>=0;i--,j++)num[j]=s[i]-'0';
        ll ans=dfs(len-1,1);
        printf("%lld\n",ans-1);
    }
    return 0;
}