zoukankan      html  css  js  c++  java
  • [日常摸鱼]loj6000「网络流 24 题」搭配飞行员

    题面

    应该是二分图匹配,不过我写的是网络最大流。

    dinic求二分图最大匹配:加个源点和汇点,源点连向二分图的一边所有点,二分图的另一边所有点连向汇点,很明显这样得到的最大流就是这个二分图的最大匹配。

    #include<cstdio>
    #include<algorithm>
    #define rep(i,n) for(register int i=1;i<=n;i++)
    #define REP(i,a,b) for(register int i=a;i<=b;i++)
    using namespace std;
    const int N=105;
    const int M=10205;
    const int INF=(~0u>>1);
    struct edge
    {
        int to,nxt,w;
        edge(int to=0,int nxt=0,int w=1):to(to),nxt(nxt),w(w){}
    }edges[M<<1];
    int n,m,cnt,st,ed,s,t,ans;
    int head[M<<1],d[N],q[N];
    inline void addEdge(int u,int v)
    {
        edges[++cnt]=edge(v,head[u]);
        head[u]=cnt;
        edges[++cnt]=edge(u,head[v],0);
        head[v]=cnt;
    }
    #define cur edges[i].to
    inline bool bfs()
    {
        rep(i,t)d[i]=0;d[s]=1;
        st=ed=0;q[st++]=s;
        while(ed<st)
        {
            int k=q[ed++];
            for(register int i=head[k];i;i=edges[i].nxt)if(edges[i].w&&!d[cur])
            {
                d[cur]=d[k]+1;q[st++]=cur;
                if(cur==t)return 1;
            }
        }
        return 0;
    }
    inline int dinic(int x,int f)
    {
        if(x==t)return f;
        int res=f;
        for(register int i=head[x];i&&res;i=edges[i].nxt)if(edges[i].w&&d[cur]==d[x]+1)
        {
            int k=dinic(cur,min(res,edges[i].w));
            if(!k)d[cur]=0;
            edges[i].w-=k;edges[i^1].w+=k;res-=k;
        }
        return f-res;
    }
    int main()
    {
        scanf("%d%d",&n,&m);s=n+1;t=n+2;cnt=1;
        int u,v;
        while(scanf("%d%d",&u,&v)==2)addEdge(u,v);
        REP(i,1,m)addEdge(s,i);
        REP(i,m+1,n)addEdge(i,t);
        int flow=0;
        while(bfs())while((flow=dinic(s,INF)))ans+=flow;
        printf("%d",ans);
        return 0;
    }
  • 相关阅读:
    03_ if 练习 _ little2big
    uva 11275 3D Triangles
    uva 12296 Pieces and Discs
    uvalive 3218 Find the Border
    uvalive 2797 Monster Trap
    uvalive 4992 Jungle Outpost
    uva 2218 Triathlon
    uvalive 3890 Most Distant Point from the Sea
    uvalive 4728 Squares
    uva 10256 The Great Divide
  • 原文地址:https://www.cnblogs.com/yoshinow2001/p/8421828.html
Copyright © 2011-2022 走看看