BZOJ2118墨墨的等式[数论 最短路建模]

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
using namespace std;
typedef long long ll;
const ll N=5*1e5+5,INF=1e19;
ll n;
ll p=INF,a[20];;
ll bmx,bmn,ans=0;
struct edge{
    ll v,w,ne;
}e[N*15];
ll h[N],cnt=0;
void ins(ll u,ll v,ll w){
    cnt++;
    e[cnt].v=v;e[cnt].w=w;e[cnt].ne=h[u];h[u]=cnt;
    //cnt++;
    //e[cnt].v=u;e[cnt].w=w;e[cnt].ne=h[v];h[v]=cnt;
}
void buildGraph(){
    for(ll i=0;i<p;i++)
        for(ll j=1;j<=n;j++){
            if(a[j]==p) continue;
            ins(i,(i+a[j])%p,a[j]);
            //prllf("ins %d %lld %lld\n",i,(i+a[j])%p,a[j]);
        }
}

struct hn{
    ll u,d;
    bool operator <(const hn &rhs)const{return d>rhs.d;}
};
ll d[N];
bool done[N];
priority_queue<hn> q;
void dijkstra(ll s){
    for(ll i=0;i<p;i++) d[i]=INF;
    d[s]=0;q.push((hn){s,0});
    while(!q.empty()){
        hn x=q.top();q.pop();
        ll u=x.u;
        if(done[u]) continue;
        done[u]=1;
        for(ll i=h[u];i;i=e[i].ne){
            ll v=e[i].v;
            if(d[v]>d[u]+e[i].w){
                d[v]=d[u]+e[i].w;
                q.push((hn){v,d[v]});
            }
        }
    }
}
int main() {
    scanf("%lld%lld%lld",&n,&bmn,&bmx);
    for(ll i=1;i<=n;i++) scanf("%lld",&a[i]),p=min(p,a[i]);
    buildGraph();
    dijkstra(0);
    for(ll i=0;i<p;i++){
        if(d[i]>bmx) continue;
        ll l=max(0LL,(bmn-d[i])/p),r=(bmx-d[i])/p;
        if(l*p+d[i]<bmn) l++;
        ans+=r-l+1;
    }
    printf("%lld",ans);
    return 0;
}