BZOJ 1799 self 同类分布(数位dp，区间各位数字和能整除原数的数字个数)

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <algorithm>
using namespace std;
typedef long long ll;

int digit[20];
ll dp[20][200][200];

ll dfs(int pos, int rem, int pre, int sum, int limit)
{
if (pos == -1) return rem == 0 && pre == sum;
if (!limit && dp[pos][rem][pre] != -1) return dp[pos][rem][pre];
if (pre > sum) return 0;
int last = limit ? digit[pos] : 9;
ll ret = 0;
for (int i = 0; i <= last; ++i) {
ret += dfs(pos - 1, (rem * 10 + i) % sum, pre + i, sum, limit && (i == last));
}
if (!limit) dp[pos][rem][pre] = ret;
return ret;
}

ll solve(ll x)
{
int len = 0;
memset(digit, 0, sizeof(digit));
while (x) {
digit[len++] = x % 10;
x /= 10;
}
ll ret = 0;
for (int i = 1; i <= 9 * len; ++i) {
memset(dp, -1, sizeof(dp));
ret += dfs(len - 1, 0, 0, i, 1);
}
return ret;
}

int main()
{
ll n, m;
while (~scanf("%lld%lld", &n, &m)) {
printf("%lld\n", solve(m) - solve(n - 1));
}
return 0;
}