HDU 不要62 2089 数位DP

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
typedef long long LL;
#define MOD  2520
int dp[20][2];//dp[数字的长度][数字的第一位数字]；
int bit[20], p = 0;

int dfs(int pos,int first,int flag)
{

if(pos == -1)
    {
        return 1;
    }

    if(!flag && dp[pos][first] != -1)
        return dp[pos][first];

    int ans = 0, end;
    end = flag?bit[pos]:9;

    for(int i=0; i<=end; i++)
    {
        if(i == 4)continue;

        if(i == 2 && first)continue;

        ans += dfs(pos-1, i == 6, flag && end == i);
    }

    if( !flag )
        dp[pos][first] = ans;

    return ans;
}


int solve(int n)
{
    int len = 0;
    while(n)
    {
        bit[len ++] = n%10;
        n /= 10;
    }
    return dfs(len-1, 0, 1);
}

int main()
{
    int a, b;
    memset(dp, -1, sizeof(dp));

    while(scanf("%d%d",&a,&b), a+b)
    {
        printf("%d\n", solve(b) - solve(a-1) );
    }
    return 0;
}