BZOJ1733: [Usaco2005 feb]Secret Milking Machine 神秘的挤奶机

n<=200个点m<=40000条边无向图，求   t次走不经过同条边的路径从1到n的经过的边的最大值   的最小值。

最大值最小--二分，t次不重边路径--边权1的最大流。

 #include<stdio.h>
 #include<string.h>
 #include<stdlib.h>
 #include<algorithm>
 //#include<iostream>
 using namespace std;

 int n,m,t;
 #define maxn 211
 #define maxm 160011
 struct Edge{int to,next,v;}edge[maxm];int first[maxn],le=;
 void in(int x,int y,int v) {Edge &e=edge[le];e.to=y;e.v=v;e.next=first[x];first[x]=le++;}
 void insert(int x,int y,int v) {in(x,y,v);in(y,x,v);}
 const int inf=0x3f3f3f3f;
 struct network
 {
     struct Edge{int to,next,cap,flow;}edge[maxm];int first[maxn],le,n,s,t;
     void clear(int n)
     {
         memset(first,,sizeof(first));
         le=;this->n=n;
     }
     void in(int x,int y,int cap) {Edge &e=edge[le];e.to=y;e.cap=cap;e.flow=;e.next=first[x];first[x]=le++;}
     void insert(int x,int y,int cap) {in(x,y,cap);in(y,x,);}
     int que[maxn],head,tail,dis[maxn],cur[maxn];
     bool bfs()
     {
         memset(dis,,sizeof(dis));
         dis[s]=;
         que[head=(tail=)-]=s;
         while (head!=tail)
         {
             const int now=que[head++];
             for (int i=first[now];i;i=edge[i].next)
             {
                 const Edge &e=edge[i];
                 if (e.cap>e.flow && !dis[e.to])
                 {
                     dis[e.to]=dis[now]+;
                     que[tail++]=e.to;
                 }
             }
         }
         return dis[t];
     }
     int dfs(int x,int a)
     {
         if (x==t || !a) return a;
         int flow=,f;
         for (int &i=cur[x];i;i=edge[i].next)
         {
             Edge &e=edge[i];
             if (dis[e.to]==dis[x]+ && (f=dfs(e.to,min(a,e.cap-e.flow)))>)
             {
                 flow+=f;
                 e.flow+=f;
                 edge[i^].flow-=f;
                 a-=f;
                 if (!a) break;
             }
         }
         return flow;
     }
     int dinic(int s,int t)
     {
         this->s=s;this->t=t;
         int ans=;
         while (bfs())
         {
             for (int i=;i<=n;i++) cur[i]=first[i];
             ans+=dfs(s,inf);
         }
         return ans;
     }
 }g;
 bool check(int x)
 {
     g.clear(n);
     for (int i=;i<=n;i++)
         for (int j=first[i];j;j=edge[j].next)
         {
             const Edge &e=edge[j];
             if (e.v<=x) g.insert(i,e.to,);
         }
     return g.dinic(,n)>=t;
 }
 int x,y,v;
 int main()
 {
     scanf("%d%d%d",&n,&m,&t);
     int Max=;
     memset(first,,sizeof(first));
     for (int i=;i<=m;i++)
     {
         scanf("%d%d%d",&x,&y,&v);
         insert(x,y,v);
         Max=max(Max,v);
     }
     int L=,R=Max+;
     while (L<R)
     {
         int mid=(L+R)>>;
         if (check(mid)) R=mid;
         else L=mid+;
     }
     printf("%d\n",L);
     return ;
 }