BZOJ 1975: [Sdoi2010]魔法猪学院

 1 #include<queue>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 int duin,N,M,next[200010],point[5010],v[200010],next2[200010],point2[5010],v2[200010];
 7 double c[200010],c2[200010],dist[5010],duif[4000010],E,sum=0;
 8 int cnt=0,cnt2=0,duiu[4000010];
 9 bool vis[5010];
10 void insect(int x,int y,double z){cnt++;next[cnt]=point[x];point[x]=cnt;v[cnt]=y;c[cnt]=z;}
11 void insect2(int x,int y,double z){cnt2++;next2[cnt2]=point2[x];point2[x]=cnt2;v2[cnt2]=y;c2[cnt2]=z;}
12 void swapp(double &x,double &y){double z=x;x=y;y=z;}
13 void swapp2(int &x,int &y){int z=x;x=y;y=z;}
14 void SPFA()
15 {
16     int i,u; queue<int>q;
17     for (i=1;i<N;++i) dist[i]=1e150; memset(vis,0,sizeof(vis));
18     dist[N]=0; vis[N]=1; q.push(N);
19     while (!q.empty())
20     {
21         u=q.front(); q.pop();
22         for (i=point2[u];i!=0;i=next2[i])
23          if (dist[v2[i]]>dist[u]+c2[i])
24          {
25              dist[v2[i]]=dist[u]+c2[i];
26              if (vis[v2[i]]==0) {vis[v2[i]]=1;q.push(v2[i]);}
27          }
28     }
29 }
30 void weihu()
31 {
32     duiu[1]=duiu[duin];duif[1]=duif[duin];duin--;
33     int i=1;
34     while (i<duin)
35     {
36         if (((i*2+1>duin)||(duif[i]<duif[i*2+1]))&&((i*2>duin)||(duif[i]<duif[i*2])))
37          return;
38         if (i*2+1<=duin)
39          if (duif[i*2+1]<duif[i*2])
40           {
41               swapp(duif[i*2+1],duif[i]);
42               swapp2(duiu[i*2+1],duiu[i]); i=i*2+1;
43           }
44          else
45           {
46               swapp(duif[i*2],duif[i]);
47               swapp2(duiu[i*2],duiu[i]); i=i*2;
48           }
49         else
50          {
51              swapp(duif[i*2],duif[i]);
52               swapp2(duiu[i*2],duiu[i]); i=i*2;
53          }
54     }
55 }
56 void indui(int u,double f)
57 {
58     duin++;duiu[duin]=u;duif[duin]=f;
59     int i=duin;
60     while (i>1)
61     {
62         if (duif[i]>duif[i/2]) return;
63         else {swapp(duif[i],duif[i/2]);swapp2(duiu[i],duiu[i/2]); i=i/2;}
64     }
65 }
66 void astar()
67 {
68     int u,i,u2; double f,g,f2,g2; cnt=0;
69     duin=1; duiu[1]=1; duif[1]=dist[1];
70     while (duin>0)
71     {
72         u=duiu[1];f=duif[1];g=f-dist[u]; weihu();
73         if (u==N){sum+=f; if (sum<=E) {cnt++;continue;} else return;}
74         for (i=point[u];i!=0;i=next[i])
75         {
76             u2=v[i]; g2=g+c[i]; f2=g2+dist[u2];
77             indui(u2,f2);
78         }
79     }
80 }
81 int main()
82 {
83     scanf("%d %d %lf\n",&N,&M,&E);
84     int i,x,y;double z;
85     for (i=1;i<=M;++i)
86     {
87         scanf("%d %d %lf\n",&x,&y,&z);
88         insect(x,y,z); insect2(y,x,z);
89     }
90     SPFA();
91     astar();
92     printf("%d\n",cnt);
93     return 0;
94 }