poj2449：第k短路问题

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cstring>
 4 #include<queue>
 5 using namespace std;
 6 #define maxn 1005
 7 #define maxm 100005
 8 #define inf 1<<29
 9 int s,t,k,n,cnt[maxn];
10 int head[maxn],ecnt,headc[maxn],vis[maxn],d[maxn];
11 struct edge{
12     int u,v,next,w;
13 }E[maxm],Ec[maxm];
14 struct Node{
15     int g,v,f;
16     Node(int x,int y,int z):f(x),g(y),v(z){}
17     bool operator < (const Node& a) const{return a.f<f;}
18 };
19 void addedge(int u,int v,int w)
20 {
21     E[++ecnt].u=u;
22     E[ecnt].v=v;
23     E[ecnt].w=w;
24     E[ecnt].next=head[u];
25     head[u]=ecnt;
26     
27     Ec[ecnt].u=v;
28     Ec[ecnt].v=u;
29     Ec[ecnt].w=w;
30     Ec[ecnt].next=headc[v];
31     headc[v]=ecnt;
32 }
33 void spfa(int x)
34 {
35     queue<int> q;
36     for(int i=1 ; i<=n ; ++i)
37         d[i]=inf;
38     d[x]=0;
39     vis[x]=1;
40     q.push(x);
41     while(!q.empty())
42     {
43         int dd=q.front();q.pop();
44         vis[dd]=0;
45         for(int i=headc[dd] ; i ; i=Ec[i].next )
46         {
47             int v=Ec[i].v;
48             int val=Ec[i].w;
49             if(d[v]>d[dd]+val)
50             {
51                 d[v]=d[dd]+val;
52                 if(!vis[v])
53                 {
54                     vis[v]=1;
55                     q.push(v);
56                 }
57             }
58         }
59     }
60 }
61 int A_star(int x)
62 {
63     if(d[x]==inf)return -1;
64     if(s==t)k++;
65     priority_queue<Node> que;
66     que.push(Node(d[x],0,x));
67     Node next(0,0,0);
68     while(!que.empty())
69     {
70         Node now=que.top();que.pop();
71         int dd=now.v;
72         cnt[dd]++;
73         if(cnt[t]==k)return now.g ;
74         if(cnt[dd]>k)continue; 
75         for(int i=head[dd] ; i ; i=E[i].next )
76         {
77             if(d[E[i].v]==inf)continue;
78             next.v=E[i].v;
79             next.g=now.g+E[i].w;
80             next.f=d[next.v]+next.g; 
81             que.push(next);
82         }
83     }
84     return -1;
85 }
86 int main()
87 {
88     int m,u,v,w;
89     scanf("%d%d",&n,&m);
90     for(int i=1 ; i<=m ; ++i )
91         {
92             scanf("%d%d%d",&u,&v,&w);
93             addedge(u,v,w);
94         }
95     scanf("%d%d%d",&s,&t,&k);
96     spfa(t);
97     printf("%d",A_star(s)); 
98     return 0;
99  }