[BZOJ2118] 墨墨的等式（最短路）

#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#define N 6000001
#define LL long long 

using namespace std;

int n, cnt;
int head[N], to[N], next[N];
LL L, R, ans, dis[N], m = ~(1 << 31), a[21], val[N];
bool vis[N];
queue <int> q;

inline LL read()
{
    LL x = 0, f = 1;
    char ch = getchar();
    for(; !isdigit(ch); ch = getchar()) if(ch == ‘-‘) f = -1;
    for(; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + ch - ‘0‘;
    return x * f;
}

inline void add(int x, int y, LL z)
{
	to[cnt] = y;
	val[cnt] = z;
	next[cnt] = head[x];
	head[x] = cnt++;
}

inline void spfa()
{
	int i, u, v;
	for(i = 0; i < m; i++) dis[i] = 1e13;
	q.push(0);
	dis[0] = 0;
	while(!q.empty())
	{
		u = q.front();
		vis[u] = 0;
		q.pop();
		for(i = head[u]; ~i; i = next[i])
		{
			v = to[i];
			if(dis[v] > dis[u] + val[i])
			{
				dis[v] = dis[u] + val[i];
				if(!vis[v])
				{
					vis[v] = 1;
					q.push(v);
				}
			}
		}
	}
}

inline LL query(LL x)
{
	int i;
	LL ans = 0;
	for(i = 0; i < m; i++)
		if(dis[i] <= x)
			ans += (x - dis[i]) / m + 1;
	return ans;
}

int main()
{
	LL x, y;
	int i, j;
	n = read();
	L = read();
	R = read();
	memset(head, -1, sizeof(head));
	for(i = 1; i <= n; i++)
	{
		a[i] = read();
		if(!a[i])
		{
			i--, n--;
			continue;
		}
		m = min(m, a[i]);
	}
	for(i = 0; i < m; i++)
		for(j = 1; j <= n; j++)
			add(i, (i + a[j]) % m, a[j]);
	spfa();
	printf("%lld\n", query(R) - query(L - 1));
	return 0;
}