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  • [国家集训队] 航班安排

    对请求拆点建图

    对于一个请求,如果 (0) 时刻可以从 (0) 机场到这里,那么 (S) 向它连边,流量 (infty),费用为 (-w)

    结束时间飞回 (0) 小于时间限制,则向着 (T) 连边,费用为 (-w)

    两两枚举所有请求,如果来得及就同理连边

    最后别忘了限制一下总流量

    跑最小费用最大流即可

    #include <bits/stdc++.h>
    using namespace std;
    
    #define int long long
    
    // Init: init() !!!!!
    // Input: make(u,v,cap,cost)
    // Solver: solve(s,t)
    // Output: ans, cost
    namespace flow {
    const int N = 100005;
    const int M = 1000005;
    const int inf = 1e+12;
    struct Edge {
        int p, c, w, nxt = -1;
    } e[N];
    int s, t, tans, ans, cost, ind, bus[N], qhead = 0, qtail = -1, qu[M],vis[N], dist[N];
    
    void graph_link(int p, int q, int c, int w) {
        e[ind].p = q;
        e[ind].c = c;
        e[ind].w = w;
        e[ind].nxt = bus[p];
        bus[p] = ind;
        ++ind;
    }
    void make(int p, int q, int c, int w) {
        graph_link(p, q, c, w);
        graph_link(q, p, 0, -w);
    }
    int dinic_spfa() {
        qhead = 0;
        qtail = -1;
        memset(vis, 0x00, sizeof vis);
        memset(dist, 0x3f, sizeof dist);
        vis[s] = 1;
        dist[s] = 0;
        qu[++qtail] = s;
        while (qtail >= qhead) {
            int p = qu[qhead++];
            vis[p] = 0;
            for (int i = bus[p]; i != -1; i = e[i].nxt)
                if (dist[e[i].p] > dist[p] + e[i].w && e[i].c > 0) {
                    dist[e[i].p] = dist[p] + e[i].w;
                    if (vis[e[i].p] == 0)
                        vis[e[i].p] = 1, qu[++qtail] = e[i].p;
                }
        }
        return dist[t] < inf;
    }
    int dinic_dfs(int p, int lim) {
        if (p == t)
            return lim;
        vis[p] = 1;
        int ret = 0;
        for (int i = bus[p]; i != -1; i = e[i].nxt) {
            int q = e[i].p;
            if (e[i].c > 0 && dist[q] == dist[p] + e[i].w && vis[q] == 0) {
                int res = dinic_dfs(q, min(lim, e[i].c));
                cost += res * e[i].w;
                e[i].c -= res;
                e[i ^ 1].c += res;
                ret += res;
                lim -= res;
                if (lim == 0)
                    break;
            }
        }
        return ret;
    }
    void solve(int _s,int _t) {
        s=_s; t=_t;
        while (dinic_spfa()) {
            memset(vis, 0x00, sizeof vis);
            ans += dinic_dfs(s, inf);
        }
    }
    void init() {
        memset(bus, 0xff, sizeof bus);
    }
    }
    
    struct query {int a,b,s,t,c;} q[205];
    int N,M,K,T,t[205][205],f[205][205];
    
    signed main() {
        ios::sync_with_stdio(false);
        cin>>N>>M>>K>>T;
        flow::init();
        for(int i=1;i<=N;i++) {
            for(int j=1;j<=N;j++) {
                cin>>t[i][j];
            }
        }
        for(int i=1;i<=N;i++) {
            for(int j=1;j<=N;j++) {
                cin>>f[i][j];
            }
        }
        for(int i=1;i<=M;i++) {
            cin>>q[i].a>>q[i].b>>q[i].s>>q[i].t>>q[i].c;
            ++q[i].a;
            ++q[i].b;
            flow::make(i,i+M,1,-q[i].c);
            if(q[i].s >= t[1][q[i].a]) {
                flow::make(2*M+1,i,1e9,f[1][q[i].a]);
            }
            if(T-q[i].t >= t[q[i].b][1]) {
                flow::make(i+M,2*M+2,1e9,f[q[i].b][1]);
            }
        }
        for(int i=1;i<=M;i++) {
            for(int j=1;j<=M;j++) {
                if(q[j].s - q[i].t >= t[q[i].b][q[j].a]) {
                    flow::make(i+M,j,1e9,f[q[i].b][q[j].a]);
                }
            }
        }
        flow::make(2*M+3,2*M+1,K,0);
        flow::solve(2*M+3,2*M+2);
        cout<<-flow::cost;
    }
    
    
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  • 原文地址:https://www.cnblogs.com/mollnn/p/12329907.html
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