E - Elevator

E - Elevator
http://codeforces.com/gym/241680/problem/E
同余最短路，从0~a-1中每一个i向(i+b)%a连一条权值为b的边，向(i+c)%a连一条权值为c的边，然后跑spfa最短路，此时d[i]表示达到x%a花费的最小的距离，这里放的只有b,c，（解释一下，b,c组合出的实际大小为x,因为x过大，数组存不下，所以表示为x%a
最后统计答案的时候ans+=1+(h-d[i])/a;当前只有b,c组合出的d[i]算一个答案,然后剩下可以用a来填充

//用最小的来做同余系比较快

 #include<iostream>
 #include<cstdio>
 #include<queue>
 #include<algorithm>
 #include<cmath>
 #include<ctime>
 #include<set>
 #include<map>
 #include<stack>
 #include<cstring>
 #define inf 2147483647
 #define INF 9187201950435737471
 #define ls rt<<1
 #define rs rt<<1|1
 #define lson ls,nl,mid,l,r
 #define rson rs,mid+1,nr,l,r
 #define N 100010
 #define For(i,a,b) for(long long i=a;i<=b;i++)
 #define p(a) putchar(a)
 #define g() getchar()

 using namespace std;
 long long h;
 long long a,b,c,ans;
 long long d[];
 queue<long long>q;
 bool vis[];

 struct node{
     long long v;
     long long n;
     node *next;
 }*e[];

 void in(long long &x){
     long long y=;
     char c=g();x=;
     while(c<''||c>''){
         if(c=='-')y=-;
         c=g();
     }
     while(c<=''&&c>=''){
         x=(x<<)+(x<<)+c-'';c=g();
     }
     x*=y;
 }
 void o(long long x){
     if(x<){
         p('-');
         x=-x;
     }
     if(x>)o(x/);
     p(x%+'');
 }

 void push(long long x,long long y,long long v){
     node *p;
     p=new node();
     p->n=y;
     p->v=v;
     if(e[x]==)
         e[x]=p;
     else{
         p->next=e[x]->next;
         e[x]->next=p;
     }
 }

 void spfa(){
      For(i,,a)
          d[i]=INF;
     q.push(%a);
     d[%a]=;
     while(!q.empty()){
         long long t=q.front();
         q.pop();
         vis[t]=true;

         for(node *i=e[t];i;i=i->next){
             if(d[i->n]>d[t]+i->v){
                 d[i->n]=d[t]+i->v;
                 if(!vis[i->n]){
                     q.push(i->n);
                     vis[i->n]=true;
                 }
             }
         }
         vis[t]=false;
     }
 }

 int main(){
      freopen("elevator.in","r",stdin);
      freopen("elevator.out","w",stdout);
     in(h);
     in(a);in(b);in(c);
     if(a>b) swap(a,b);
     if(a>c) swap(a,c);
     For(i,,a-){
         push(i,(i+b)%a,b);
         push(i,(i+c)%a,c);
     }
     spfa();
     For(i,,a-)
         if(h>=d[i])
             ans+=+(h-d[i])/a;
     o(ans);
     return ;
 }