• UVA735 TLE&&WA,,,,悲剧未完成,最大流


    题目点这
    题意:输入n,有n个插座,下面n行是每个插座的类型(最后24个字母来表示一个插座,没有空格放心用scanf,但是有可能插座会相同,但是这个没有什么影响)
    输入m,有m个电器,下面m行每行两个单词分别是电器的名字和插头类型(同样24个字母单词内没空格,两个单词空格隔开)
    输入k,有k个转换器,下面k行每行两个单词,分别表示转换器的入口类型和插头类型
    每种转换器的个数是无限的,转换器本身可以与转换器相连
    要你求,让最多的电器能够插在插座上(可以用转换器辅助也可以直接插上去),输入不能插上去的电器的数量

    分析
    电器从1到m标号,转换器从m+1到m+k标号,插座从m+k+1到m+k+n标号,另外设置一个源点s=0,汇点t=m+k+n+1 , 求s到t的最大流s与所有电器建一条有向边,容量为1,所有插座与汇点建一条有向边,容量为1。对于每个电器,如果能直接和插座相连的,和每个能相连的插座建一条有向边,容量为1.另外,所有电器和所有能连接上的转换器建一条有向边,容量为INF,转换器和转换器之间能相连的建一条有向边容量为INF,转换器和插座能相连建一条有向边容量为INF。

    写了一下午,,,WA,伤心
    还不知道发生了什么

    #include<queue>
    #include<cstdio>
    #include<vector>
    #include<string>
    #include<cstring>
    #include<iostream>
    using namespace std;
    const int N=400,INF=999999;
    struct Edge{
        int from,to,cap,flow;
        Edge(int u,int v,int c,int f):from(u),to(v),cap(c),flow(f){}
    };
    int s,t,n,m,k;
    string st,device[N],plug[N],adapter1[N],adapter2[N];
    vector<Edge>edges;
    vector<int>G[N];//邻接表
    bool vis[N];//use when bfs
    int d[N],cur[N];//dist,now edge
    
    void AddEdge(int from,int to,int cap){
        edges.push_back(Edge(from,to,cap,0));
        edges.push_back(Edge(to,from, 0 ,0));
        int top=edges.size();
        G[from].push_back(top-2);
        G[ to ].push_back(top-1);
    }
    
    bool BFS(){
        memset(vis,0,sizeof(vis));
        queue<int>Q;
        Q.push(s);d[s]=0;vis[s]=1;
        while (!Q.empty()){
            int x=Q.front();Q.pop();
            for (int i=0;i<G[x].size();i++){
                Edge& e=edges[G[x][i]];
                if (vis[e.to]||e.cap<=e.flow)continue;
                vis[e.to]=1;d[e.to]=d[x]+1;
                Q.push(e.to);
            }
        }
        return vis[t];
    }
    
    int DFS(int x,int a){
        if (x==t||a==0)return a;
        int flow = 0,f;
        for (int& i=cur[x];i<G[x].size();i++){
            Edge& e=edges[G[x][i]];
            if (d[x]+1!=d[e.to])continue;
            if ((f=DFS(e.to,min(a,e.cap-e.flow)))<=0)continue;
            e.flow+=f;
            edges[G[x][i]^1].flow-=f;
            flow+=f; a-=f;
            if (a==0)break;
        }
        return flow;
    }
    
    int Maxflow(int s,int t){
        int flow=0;
        while(BFS()){
            memset(cur,0,sizeof(cur));
            flow+=DFS(s,INF);
        }
        return flow;
    }
    
    int main(){
        freopen("fuck.in","r",stdin);
        int T;scanf("%d",&T);
        for (int cas=1;cas<=T;cas++){
            edges.clear();
            for (int i=1;i<N;i++)G[i].clear();
            scanf("%d
    ",&n);//n个插座
            for (int i=1;i<=n;i++)cin>>plug[i];
            scanf("%d
    ",&m);//m个设备 
            for (int i=1;i<=m;i++)cin>>st>>device[i];
            scanf("%d
    ",&k);//k种转换器 
            for (int i=1;i<=k;i++)cin>>adapter1[i]>>adapter2[i];
    
            s=0;t=m+k+n+1;
            for (int i=1;i<=m;i++){
                AddEdge(0,i,1);
                for (int j=1;j<=n;j++)
                  if (device[i]==plug[j])AddEdge(i,m+k+j,1);
                for (int j=1;j<=k;j++)
                  if (device[i]==adapter1[j])AddEdge(i,m+j,INF);
            }
            for (int i=1;i<=k;i++){
                for (int j=1;j<=n;j++)
                  if (adapter2[i]==plug[j])AddEdge(m+i,m+k+j,INF);
                for (int j=1;j<=k;j++)
                  if (i!=j&&adapter2[i]==adapter1[j])AddEdge(m+i,m+j,INF);
            }
            for (int i=1;i<=n;i++)AddEdge(m+k+i,t,1);
    
            int flow=Maxflow(s,t);
            if (cas==T)printf("%d
    ",m-flow);
            else printf("%d
    
    ",m-flow);
        }
        return 0;
    }

    然后改成EK算法,又tle了。。。。

    #include<queue>
    #include<cstdio>
    #include<vector>
    #include<string>
    #include<cstring>
    #include<iostream>
    using namespace std;
    const int N=400,INF=999999;
    struct Edge{
        int from,to,cap,flow;
        Edge(int u,int v,int c,int f):from(u),to(v),cap(c),flow(f){}
    };
    int s,t,n,m,k,a[N],p[N];
    string st,device[N],plug[N],adapter1[N],adapter2[N];
    vector<Edge>edges;
    vector<int>G[N];//邻接表
    bool vis[N];//use when bfs
    
    void AddEdge(int from,int to,int cap){
        edges.push_back(Edge(from,to,cap,0));
        edges.push_back(Edge(to,from, 0 ,0));
        int top=edges.size();
        G[from].push_back(top-2);
        G[ to ].push_back(top-1);
    }
    
    int Maxflow(int s,int t){
        int flow=0;
        for(;;){
            memset(a,0,sizeof(a));
            queue<int>Q;
            Q.push(s);a[s]=INF;
            while(!Q.empty()){
                int x=Q.front();Q.pop();
                for (int i=0;i<G[x].size();i++){
                    Edge& e=edges[G[x][i]];
                    if (a[e.to]||e.cap<=e.flow)continue;
                    //printf("edge:from %d to %d cap %d flow %d
    ",e.from,e.to,e.cap,e.flow);
                    p[e.to]=G[x][i];
                    a[e.to]=min(a[x],e.cap-e.flow);
                    Q.push(e.to);
                }
                if (a[t])break;
            }
            if (!a[t])break;
            for (int x=t;x!=s;x=edges[p[x]].from){
                edges[p[x]  ].flow+=a[t];
                edges[p[x]^1].flow-=a[t];
            }
            flow+=a[t];
        }
        //printf("flow=%d
    ",flow);
        return flow;
    }
    
    int main(){
        freopen("fuck.in","r",stdin);
        int T;scanf("%d",&T);
        for (int cas=1;cas<=T;cas++){
            edges.clear();
            for (int i=1;i<N;i++)G[i].clear();
            scanf("%d
    ",&n);//n个插座
            for (int i=1;i<=n;i++)cin>>plug[i];
            scanf("%d
    ",&m);//m个设备 
            for (int i=1;i<=m;i++)cin>>st>>device[i];
            scanf("%d
    ",&k);//k种转换器 
            for (int i=1;i<=k;i++)cin>>adapter1[i]>>adapter2[i];
    
            s=0;t=m+k+n+1;
            for (int i=1;i<=m;i++){
                AddEdge(0,i,1);
                for (int j=1;j<=n;j++)
                  if (device[i]==plug[j])AddEdge(i,m+k+j,1);
                for (int j=1;j<=k;j++)
                  if (device[i]==adapter1[j])AddEdge(i,m+j,INF);
            }
            for (int i=1;i<=k;i++){
                for (int j=1;j<=n;j++)
                  if (adapter2[i]==plug[j])AddEdge(m+i,m+k+j,INF);
                for (int j=1;j<=k;j++)
                  if (i!=j&&adapter2[i]==adapter1[j])AddEdge(m+i,m+j,INF);
            }
            for (int i=1;i<=n;i++)AddEdge(m+k+i,t,1);
    
            int flow=Maxflow(s,t);
            if (cas==T)printf("%d
    ",m-flow);
            else printf("%d
    
    ",m-flow);
        }
        return 0;
    }

    要开数组模拟存图吗,有功夫以后试试,心累
    若有神犇路过,,您懂的

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  • 原文地址:https://www.cnblogs.com/cww97/p/12349431.html
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