【luogu1462】通往奥格瑞玛的道路 (最短路)(spfa)

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int N=10000+5,inf=1e9;
 4 int n,m,blo,w[N],ww[N];
 5 inline int rd()
 6 {
 7     int x=0,w=0;char ch=0;
 8     while(!isdigit(ch)) w|=ch==‘-‘,ch=getchar();
 9     while(isdigit(ch)) x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
10     return w?-x:x;
11 }
12 int head[N],cnt=0;
13 struct edge
14 {
15     int v,nxt,sh;
16 }e[N*5*2];
17 void add(int u,int v,int sh)
18 {
19     e[++cnt].v=v;
20     e[cnt].sh=sh;
21     e[cnt].nxt=head[u];
22     head[u]=cnt;
23 }
24 
25 int vis[N],blood[N];
26 bool spfa(int k)
27 {
28     memset(vis,0,sizeof(vis));
29     for(int i=0;i<=n;i++) blood[i]=inf;
30     deque<int> q;
31     q.push_back(1);
32     vis[1]=1,blood[1]=0;
33     while(!q.empty())
34     {
35         int u=q.front();
36         q.pop_front();vis[u]=0;
37         for(int i=head[u];i;i=e[i].nxt)
38         {
39             int v=e[i].v,sh=e[i].sh;
40             if(blood[v]>blood[u]+sh&&w[v]<=k)
41             {
42                 blood[v]=blood[u]+sh;
43                 if(!vis[v])
44                 {
45                     if(!q.empty()&&blood[v]<=blood[q.front()]) q.push_front(v);
46                     else q.push_back(v);
47                     vis[v]=1;    
48                 }
49             }
50         }
51     }
52     if(blood[n]>blo) return 0;
53     else return 1;
54 }
55 
56 int main()
57 {
58     memset(head,0,sizeof(head));
59     n=rd(),m=rd(),blo=rd();
60     for(int i=1;i<=n;i++) w[i]=rd(),ww[i]=w[i];
61     for(int i=1;i<=m;i++)
62     {
63         int u=rd(),v=rd(),sh=rd();
64         add(u,v,sh);add(v,u,sh);
65     }
66     if(!spfa(inf)) printf("AFK");
67     else
68     {
69         int l=1,r=n;
70         sort(ww+1,ww+1+n);//
71         while(l<=r)
72         {
73             int mid=(l+r)>>1;
74             if(spfa(ww[mid])) r=mid-1;
75             else l=mid+1;
76         }
77         printf("%d",ww[l]);
78     }
79     return 0;
80 }