bzoj2662：[BeiJing wc2012]冻结

 1 #include<cstdio>
 2 #include<algorithm>
 3 #include<cstring>
 4 #include<queue>
 5 #define maxn 55
 6 #define maxm 1005
 7 #define inf 1<<29
 8 using namespace std;
 9 int head[maxn],d[maxn][maxn];
10 bool vis[maxn][maxn];
11 int ecnt,n,m,k,ans=inf;
12 struct edge{
13     int u,v,w,next;
14 }E[maxm<<1];
15 struct node{
16     int num,knum;
17     node(int x,int y):num(x),knum(y){}
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 void spfa()
28 {
29     queue<node> q;
30     memset(d,127/3,sizeof(d));
31     d[1][0]=0;vis[1][0]=1;
32     node now(1,0);
33     q.push(now);
34     while(!q.empty())
35     {
36         node now=q.front();q.pop();
37         int dd=now.num;
38         int kk=now.knum;
39         vis[dd][kk]=0;
40         for(int i=head[dd] ; i ; i=E[i].next )
41         {
42             int v=E[i].v;
43             int w=E[i].w;
44             if(d[v][kk]>d[dd][kk]+w)
45             {
46                 d[v][kk]=d[dd][kk]+w;
47                 if(!vis[v][kk])
48                 {
49                     vis[v][kk]=1;
50                     q.push(node(v,kk));
51                 }
52             }
53             if(d[v][kk+1]>d[dd][kk]+(w>>1)&&kk<k)
54             {
55                 d[v][kk+1]=d[dd][kk]+(w>>1);
56                 if(!vis[v][kk+1])
57                 {
58                     vis[v][kk+1]=1;
59                     q.push(node(v,kk+1));
60                 }
61             }
62         }
63     }
64     for(int i=1 ; i<=k ; ++i)ans=min(ans,d[n][i]);
65     printf("%d",ans);
66 }
67 int main()
68 {
69     int u,v,w;
70     scanf("%d%d%d",&n,&m,&k);
71     for(int i=1 ; i<=m ; ++i )
72     {
73         scanf("%d%d%d",&u,&v,&w);
74         addedge(u,v,w);
75         addedge(v,u,w);
76     }
77     spfa();
78     return 0;
79 }