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  • HDU 5855 Less Time, More profit

    二分t+最大权闭合图。

    很显然二分那个t作为limit。每一个limit下,有一些边不能用了,然后要知道这种情况下怎么选点获得的价值最大。

    这么想:一个shop想获得收益,就必须选择某一些plant,问题就转化成了最大权闭合图。

    #pragma comment(linker, "/STACK:1024000000,1024000000")
    #include<cstdio>
    #include<cstring>
    #include<cmath>
    #include<algorithm>
    #include<vector>
    #include<map>
    #include<set>
    #include<queue>
    #include<stack>
    #include<iostream>
    using namespace std;
    typedef long long LL;
    const double pi=acos(-1.0),eps=1e-8;
    void File()
    {
        freopen("D:\in.txt","r",stdin);
        freopen("D:\out.txt","w",stdout);
    }
    template <class T>
    inline void read(T &x)
    {
        char c = getchar(); x = 0;while(!isdigit(c)) c = getchar();
        while(isdigit(c)) { x = x * 10 + c - '0'; c = getchar();  }
    }
    
    int T,n,m;
    int L;
    struct X
    {
        int pay;
        int t;
    }p[300];
    vector<int>g[300];
    int pro[300];
    bool flag[300],se[300];
    
    const int maxn = 3000 + 10;
    const int INF = 0x7FFFFFFF;
    struct Edge
    {
        int from, to, cap, flow;
        Edge(int u, int v, int c, int f) :from(u), to(v), cap(c), flow(f){}
    };
    vector<Edge>edges;
    vector<int>G[maxn];
    bool vis[maxn];
    int d[maxn];
    int cur[maxn];
    int s, t;
    
    void init()
    {
        for (int i = 0; i < maxn; i++)
            G[i].clear();
        edges.clear();
    }
    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 w = edges.size();
        G[from].push_back(w - 2);
        G[to].push_back(w - 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)
                {
                    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]&&(f=DFS(e.to,min(a,e.cap-e.flow)))>0)
            {
                edges[G[x][i]].flow+=f;
                edges[G[x][i] ^ 1].flow-=f;
                flow+=f;
                a-=f;
                if(a==0) break;
            }
        }
        if(!flow) d[x] = -1;
        return flow;
    }
    int dinic(int s, int t)
    {
        int flow = 0;
        while (BFS())
        {
            memset(cur, 0, sizeof(cur));
            flow += DFS(s, INF);
        }
        return flow;
    }
    
    
    int check(int limit)
    {
        memset(flag,0,sizeof flag);
        memset(se,0,sizeof se);
        for(int i=1;i<=n;i++) if(p[i].t<=limit) flag[i]=1;
    
        init();
    
        s=0; t=n+m+1;
    
        int sum=0;
    
        for(int i=1;i<=m;i++)
        {
            bool fail=0;
            for(int j=0;j<g[i].size();j++)  if(flag[g[i][j]]==0) fail=1;
            if(fail==1) continue;
    
            for(int j=0;j<g[i].size();j++) AddEdge(i,g[i][j]+m,INF);
    
            AddEdge(s,i,pro[i]);
            sum=sum+pro[i];
        }
    
        for(int i=1;i<=n;i++) AddEdge(i+m,t,p[i].pay);
    
        return sum-dinic(s,t);
    }
    
    int main()
    {
        //File();
        scanf("%d",&T); int cas=1;
        while(T--)
        {
            scanf("%d%d%d",&n,&m,&L);
            for(int i=0;i<=m;i++) g[i].clear();
            for(int i=1;i<=n;i++) scanf("%d%d",&p[i].pay,&p[i].t);
            for(int i=1;i<=m;i++)
            {
                scanf("%d",&pro[i]);
                int k; scanf("%d",&k);
                while(k--)
                {
                    int x; scanf("%d",&x);
                    g[i].push_back(x);
                }
            }
            int left=0,right=1000000000;
    
            int ans1=-1,ans2=-1;
            while(left<=right)
            {
                int mid=(left+right)/2;
                int ppp=check(mid);
                if(ppp>=L)
                {
                    right=mid-1;
                    ans1=mid;
                    ans2=ppp;
                }
                else
                    left=mid+1;
            }
            printf("Case #%d: ",cas++);
            if(ans1==-1) printf("impossible
    ");
            else printf("%d %d
    ",ans1,ans2);
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/zufezzt/p/5788708.html
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