图论(A*算法，K短路) ：POJ 2449 Remmarguts' Date

 1 #include <iostream>
 2 #include <algorithm>
 3 #include <cstdio>
 4 #include <cstring>
 5 #include <queue>
 6 using namespace std;
 7 
 8 const int MAXN=1010,MAXM=100010;
 9 int cnt,fir[MAXN],nxt[MAXM],to[MAXM],val[MAXM];
10 int rcnt,rfir[MAXN],rnxt[MAXM],rto[MAXM],rval[MAXM];
11 int dis[MAXN];
12 struct A{
13     int f,g,dot;
14     bool operator <(const A a)const{
15         return a.f<f;
16     }
17 };
18 
19 void raddedge(int a,int b,int v)
20 {
21     rnxt[++rcnt]=rfir[a];rto[rcnt]=b;rfir[a]=rcnt;rval[rcnt]=v;
22 }
23 
24 void addedge(int a,int b,int v)
25 {
26     nxt[++cnt]=fir[a];to[cnt]=b;fir[a]=cnt;val[cnt]=v;
27     raddedge(b,a,v);
28 }
29 int vis[MAXN];
30 void Spfa(int src)
31 {
32     queue<int>q;
33     memset(dis,127,sizeof(dis));
34     memset(vis,0,sizeof(vis));
35     dis[src]=0;vis[src]=1;q.push(src);
36     while(!q.empty())
37     {
38         int node=q.front();q.pop();vis[node]=0;
39         for(int i=rfir[node];i;i=rnxt[i])
40             if(dis[rto[i]]>dis[node]+rval[i]){
41                 dis[rto[i]]=dis[node]+rval[i];
42                 if(!vis[rto[i]])
43                     q.push(rto[i]);
44                 vis[rto[i]]=1;
45             }
46     }
47 }
48 
49 int Astar(int s,int t,int k)
50 {
51     int cont=0;
52     priority_queue<A>Q;
53     if(dis[s]==dis[0])return -1;
54     if(s==t)k++;
55     Q.push((A){dis[s],0,s});
56     A node;
57     while(!Q.empty())
58     {
59         node=Q.top();Q.pop();
60         if(node.dot==t&&++cont==k)
61             return node.f;
62         for(int i=fir[node.dot];i;i=nxt[i])
63             Q.push((A){dis[to[i]]+node.g+val[i],node.g+val[i],to[i]});
64     }
65     return -1;
66 }
67 
68 void Init()
69 {
70     cnt=rcnt=0;
71     memset(fir,0,sizeof(fir));
72     memset(rfir,0,sizeof(rfir));
73 }
74 int main()
75 {
76     int x,y,k,n,m,v,s,t;
77     while(~scanf("%d%d",&n,&m)){
78         Init();
79         for(int i=1;i<=m;i++){
80             scanf("%d%d%d",&x,&y,&v);
81             addedge(x,y,v);
82         }
83         scanf("%d%d%d",&s,&t,&k);
84         Spfa(t);
85         printf("%d\n",Astar(s,t,k));
86     }
87     return 0;
88 }