bzoj2561

  1 #include<bits/stdc++.h>
  2 #define lowbit(a) ((a)&(-(a)))
  3 #define clr(a,x) memset(a,x,sizeof(a))
  4 #define rep(i,l,r) for(int i=l;i<(r);i++)
  5 #define Rep(i,a) rep(i,cur[a],G[a].size())
  6 typedef long long ll;
  7 using namespace std;
  8 int read()
  9 {
 10     char c=getchar();
 11     int ans=0,f=1;
 12     while(!isdigit(c)){
 13         if(c==‘-‘) f=-1;
 14         c=getchar();
 15     }
 16     while(isdigit(c)){
 17         ans=ans*10+c-‘0‘;
 18         c=getchar();
 19     }
 20     return ans*f;
 21 }
 22 struct Edge{
 23     int from,to,d;
 24 };
 25 struct edge{
 26     int to,w;
 27 };
 28 const int maxn=200009,inf=0x7fffffff;
 29 int ans=0,n,m,u,v,l,cnt,d[maxn],p[maxn],cur[maxn];
 30 vector<int>G[maxn];
 31 Edge E[maxn];
 32 edge e[maxn<<1];
 33 void addedge(int d){
 34     rep(i,1,n+1) G[i].erase(G[i].begin(),G[i].end());
 35     cnt=0;
 36     rep(i,0,m){
 37         if(d*E[i].d>d*l){
 38             edge ed;
 39             ed.to=E[i].to,ed.w=1;
 40             e[cnt]=ed;G[E[i].from].push_back(cnt++);
 41             ed.to=E[i].from;
 42             e[cnt]=ed;G[E[i].to].push_back(cnt++);
 43         }
 44     }
 45 }
 46 bool bfs(){
 47     queue<int>Q;clr(p,0);
 48     rep(i,1,n+1) d[i]=inf;
 49     d[u]=0;p[u]=1;
 50     Q.push(u);
 51     while(!Q.empty()){
 52         int x=Q.front();Q.pop();p[x]=0;
 53         Rep(i,x){
 54             int t=G[x][i];
 55             if(e[t].w==0||d[e[t].to]<=d[x]+1) continue;
 56             d[e[t].to]=d[x]+1;
 57             if(!p[e[t].to]){
 58                 Q.push(e[t].to);
 59                 p[e[t].to]=1;
 60             }
 61         }
 62     }
 63     return d[v]!=inf;
 64 }
 65 int dfs(int k,int f){
 66     int flow=0;
 67     if(k==v||f==0) return f;
 68     Rep(i,k){
 69         int t=G[k][i];
 70         if(e[t].w==0||d[e[t].to]!=d[k]+1) continue;
 71         int w=dfs(e[t].to,min(e[t].w,f));
 72         if(w){
 73             e[t].w-=w;
 74             if(e[t].w) cur[i]=i;
 75             e[t^1].w+=w;
 76             flow+=w;
 77             f-=w;
 78             if(!f) break;
 79         }
 80     }
 81     return flow;
 82 }
 83 int dinic(){
 84     int ans=0;
 85     while(bfs()){
 86         clr(cur,0);
 87         ans+=dfs(u,inf);
 88     }
 89     return ans;
 90 }
 91 int main()
 92 {    
 93     n=read(),m=read();
 94     rep(i,0,m) E[i].from=read(),E[i].to=read(),E[i].d=read();
 95     u=read(),v=read(),l=read();
 96     addedge(-1);
 97     ans+=dinic();
 98     addedge(1);
 99     ans+=dinic();
100     printf("%d\n",ans);
101     return 0;
102 }