HDU 3652 B-number （数位dp）

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <algorithm>
#define MOD 1000000007
#define INF 0x7fffffff
using namespace std;
typedef long long ll;
int bit[15];
ll f[15][5][20];

ll dp(int pos, int sta, int flag, int left)
{
//第len到pos+1位已确定，现在确定第pos位
//sta=1，前面包含了序列13
//flag=1，不论第pos位为什么都比n小
//第len到pos+1组成的数除以13余left
if(pos == 0) return (sta == 2 && left == 0);
if(flag && f[pos][sta][left] != -1) return f[pos][sta][left];
ll ans = 0;
int x = flag ? 9 : bit[pos];
for(int i = 0; i <= x; i++)
{
if(sta == 2 || (sta == 1 && i == 3))
{
ans += dp(pos - 1, 2, flag || i < x, (left * 10 + i) % 13);
}
else if(i == 1)
{
ans += dp(pos - 1, 1, flag || i < x, (left * 10 + i) % 13);
}
else
{
ans += dp(pos - 1, 0, flag || i < x, (left * 10 + i) % 13);
}
}
if(flag) f[pos][sta][left] = ans;
return ans;
}

ll cal(ll n)
{
int len = 0;
while(n)
{
bit[++len] = n % 10;
n /= 10;
}
ll ans = dp(len, 0, 0, 0);
return ans;
}

int main()
{
#ifdef LOCAL
freopen("dpdata.txt", "r", stdin);
#endif

ll n;
memset(f, -1, sizeof(f));
while(scanf("%I64d", &n) != EOF)
{
printf("%I64d\n", cal(n));
}

return 0;
}