【luogu P3063 [USACO12DEC]牛奶的路由Milk Routing】 题解

题目链接：https://www.luogu.org/problemnew/show/P3063#sub

我很好奇这道题为什么没被收入SPFA好题

 #include <cstdio>
 #include <cstring>
 #include <queue>
 #include <algorithm>
 using namespace std;
 const int maxn = ;
 const int inf = 0x7fffffff-;
 int n, m, s, f, x, k, ans = inf, dis[maxn], c[maxn];
 bool vis[maxn];
 struct edge{
     int to, next, len, from, l;
 }e[maxn];
 int head[maxn], cnt;
 void add(int u, int v, int w, int l)
 {
     e[++cnt].from = u;
     e[cnt].to = v;
     e[cnt].len = w;
     e[cnt].l = l;
     e[cnt].next = head[u];
     head[u] = cnt;
 }
 int SPFA(int k)
 {
     queue<int> q;
     memset(vis,,sizeof(vis));
     memset(dis,,sizeof(dis));
     dis[s] = ;
        q.push(s);
     vis[s] = ;
     while(!q.empty())
     {
         int now = q.front();
         q.pop();
         vis[now] = ;
         for(int i = head[now]; i ; i = e[i].next)
         {
             if(dis[e[i].to] > dis[now]+e[i].len && e[i].l >= k)
             {
                 dis[e[i].to] = dis[now]+e[i].len;
                 if(!vis[e[i].to])
                 {
                     vis[e[i].to] = ;
                     q.push(e[i].to);
                 }
             }
         }
     }
 }
 int main()
 {
     scanf("%d%d%d",&n,&m,&x);
     for(int i = ; i <= m; i++)
     {
         int u,v,w,l;
         scanf("%d%d%d%d",&u,&v,&w,&l);
         add(u,v,w,l);
         add(v,u,w,l);
         c[i] = l;
     }
     sort(c+,c+m+);
     s = , f = n;
     for(int i = ; i <= m; i++)
     {
         SPFA(c[i]);
         ans = min(ans, dis[f]+x/c[i]);
     }
     printf("%d",ans);
 }