LA3231 Fair Share 二分_网络流

Code:

#include<cstdio>
#include<vector>
#include<queue>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=50004;
const int INF=10000000;
# define  pb push_back
int N,M;
int s,t;
struct Edge{
	int from,to,cap;
	Edge(int u,int v,int c):from(u),to(v),cap(c) {}
};
struct Dicnic{
   vector<Edge>edges;
   vector<int>G[maxn];
   int d[maxn],vis[maxn],cur[maxn];
   queue<int>Q;
   void init(){
   	for(int i=0;i<maxn;++i)G[i].clear();
   	edges.clear();
   }
   void addedge(int u,int v,int c){
   	edges.pb(Edge(u,v,c));               //正向弧
   	edges.pb(Edge(v,u,0));               //反向弧
   	int m=edges.size();
   	G[u].pb(m-2);
   	G[v].pb(m-1);
   }
   int BFS()
   {
    memset(vis,0,sizeof(vis));
    d[s]=0,vis[s]=1;Q.push(s);
    while(!Q.empty()){
    	int u=Q.front();Q.pop();
    	int sz=G[u].size();
    	for(int i=0;i<sz;++i){
    		Edge e=edges[G[u][i]];
    		if(!vis[e.to]&&e.cap>0){
    			d[e.to]=d[u]+1,vis[e.to]=1;
    			Q.push(e.to);
    		}
    	}
    }
    return vis[t];
   }
   int dfs(int x,int a){
       if(x==t)return a;
       int sz=G[x].size();
       int f,flow=0;
       for(int i=cur[x];i<sz;++i){
       	Edge e=edges[G[x][i]];
          cur[x]=i;
       	if(d[e.to]==d[x]+1&&e.cap>0){
       		f=dfs(e.to,min(a,e.cap));
       		if(f)
       		{
       			int u=G[x][i];
       			a-=f;
                    edges[u].cap-=f;
                    edges[u^1].cap+=f;
                    flow+=f;
                    if(a==0)break;
       		}
       	}
       }
       return flow;
   }
   int maxflow(){
   	int ans=0;
   	while(BFS()){
         memset(cur,0,sizeof(cur));
         ans+=dfs(s,INF);
   	}
   	return ans;
   }
   int check(int x)
   {
   	 int siz=G[0].size();
      for(int i=0;i<siz;++i)edges[G[s][i]].cap=1,edges[G[s][i]^1].cap=0;
      for(int i=1;i<=M;++i)
      {
      	int sz=G[i].size();
      	for(int j=0;j<sz;++j)
      	{
      		int v=edges[G[i][j]].to;
      		if(v!=s){
      			edges[G[i][j]].cap=1,edges[G[i][j]^1].cap=0;
      		}
      	}
      }
      for(int i=M+1;i<=N+M;++i)
      {
      	int sz=G[i].size();
      	for(int j=0;j<sz;++j)
      	{
      		int v=edges[G[i][j]].to;
      		if(v==t){
      			edges[G[i][j]].cap=x,edges[G[i][j]^1].cap=0;
      		}
      	}
      }
      int uu=maxflow();
      if(uu==M)return 1;
      return 0;
   }
   int operate()
   {
   	 int L=0,R=12000;
   	 int fin=0;
   	 while(L<=R)
   	 {
          int mid=(L+R)/2;
          if(check(mid)){fin=mid,R=mid-1;}
          else L=mid+1;
   	 }
      return fin;
   }
}op;
int main()
{
	//freopen("in.txt","r",stdin);
	int T;
	scanf("%d",&T);
	while(T--)
	{
		op.init();
		scanf("%d%d",&N,&M);
          s=0,t=N+M+1;
          for(int i=1;i<=M;++i)op.addedge(s,i,1);
		for(int i=1;i<=M;++i){
			int a,b;
			scanf("%d%d",&a,&b);
			a+=M,b+=M;
			op.addedge(i,a,1);
			op.addedge(i,b,1);
		}
		for(int i=M+1;i<=N+M;++i)op.addedge(i,t,0);
		printf("%d
",op.operate());
	}
     return 0;
}