hdu3709

枚举+数位dp

注意处理数字为0和1的情况。

#include <cstdio>
#include <cstring>
using namespace std;

#define D(x) 

const int MAX_DIGIT = ;

long long n;
int f[MAX_DIGIT];
long long memoize[MAX_DIGIT][**];
int pivot;

int to_digits(long long a)
{
    int ret = ;
    while (a > )
    {
        f[++ret] = a % ;
        a /= ;
    }
    return ret;
}

long long dfs(int digit, bool less, int weight)
{
    if (digit <= )
    {
        return weight == ;
    }
    if (less && memoize[digit][weight] != -)
    {
        return memoize[digit][weight];
    }
    int limit = less ?  : f[digit];
    long long ret = ;
    for (int i = ; i <= limit; i++)
    {
        int new_weight = weight + (digit - pivot) * i;
        if (new_weight < )
        {
            continue;
        }
        ret += dfs(digit - , less || i < f[digit], new_weight);
    }
    memoize[digit][weight] = ret;
    return ret;
}

long long work(long long n)
{
    if (n < )
    {
        return ;
    }
    int len = to_digits(n);
    long long ret = ;
    for (int i = ; i <= len; i++)
    {
        pivot = i;
        memset(memoize, -, sizeof(memoize));
        ret += dfs(len, false, );
    }
    return ret - len + ;
}

int main()
{
    int t;
    scanf("%d", &t);
    while (t--)
    {
        long long a, b;
        scanf("%lld%lld", &a, &b);
        printf("%lld\n", work(b) - work(a - ));
    }
    return ;
}