HDU 2089 不要62 数位DP入门

#include<cstdio>
#include<cstring>
#include<algorithm>

using namespace std;

const int maxn=8;

int a[maxn];
int dp[maxn][2];

int dfs(int len,bool state,bool e)
{
    if(!len)
        return 1;
    if(e&&dp[len][state]!=-1)
        return dp[len][state];

    int last=e?9:a[len];
    int ret=0;
    for(int i=0;i<=last;i++){
        if(i==4 || state && i==2)
            continue;
        ret+=dfs(len-1,i==6,e||i<a[len]);
    }
    return dp[len][state]=ret;
}

int solve(int n)
{
    memset(dp,-1,sizeof dp);
    int len=0;
    while(n){
        a[++len]=n%10;
        n/=10;
    }
    return dfs(len,false,false);
}

int main()
{
    int n,m;
    while(scanf("%d %d",&n,&m)){
        if(!n&&!m)
            break;
        printf("%d\n",solve(m)-solve(n-1));
    }
    return 0;
}