P3381 【模板】最小费用最大流

P3381 【模板】最小费用最大流

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 const int maxn = 10005, inf = 0x3f3f3f3f;
 4 struct Edge {
 5     int from, to, cap, flow, cost;
 6 };
 7 
 8 struct MCMF {
 9     int n, m, s, t;
10     vector<Edge> edges;
11     vector<int> G[maxn];
12     int inq[maxn];
13     int d[maxn];
14     int p[maxn];
15     int a[maxn];
16 
17     void init(int n) {
18         this->n = n;
19         for (int i = 1; i <= n; ++i) G[i].clear();
20         edges.clear();
21     }
22 
23     void AddEdge(int from, int to, int cap, int cost) {
24         edges.push_back((Edge){from, to, cap, 0, cost});
25         edges.push_back((Edge){to, from, 0, 0, -cost});
26         m = edges.size();
27         G[from].push_back(m-2);
28         G[to].push_back(m-1);
29     }
30     bool BellmanFord(int s, int t, int& flow, int& cost) {
31         for (int i = 1; i <= n; ++i) d[i] = inf;
32         memset(inq, 0, sizeof(inq));
33         d[s] = 0; inq[s] = 1; p[s] = 0; a[s] = inf;
34 
35         queue<int> que;
36         que.push(s);
37         while (!que.empty()) {
38             int u = que.front(); que.pop();
39             inq[u] = 0;
40             for (int i = 0; i < G[u].size(); ++i) {
41                 Edge& e = edges[G[u][i]];
42                 if (e.cap > e.flow && d[e.to] > d[u] + e.cost) {
43                     d[e.to] = d[u] + e.cost;
44                     p[e.to] = G[u][i];
45                     a[e.to] = min(a[u], e.cap-e.flow);
46                     if (!inq[e.to]) { que.push(e.to); inq[e.to] = 1; }
47                 }
48             }
49         }
50         if (d[t] == inf) return false;
51         flow += a[t];
52         cost += d[t] * a[t];
53         int u = t;
54         while (u != s) {
55             edges[p[u]].flow += a[t];
56             edges[p[u]^1].flow -= a[t];
57             u = edges[p[u]].from;
58         }
59         return true;
60     }
61     pair<int,int> mincost(int s, int t) {
62         int flow = 0, cost = 0;
63         while (BellmanFord(s, t, flow, cost));
64         return make_pair(flow,cost);
65     }
66 }mcmf;
67 int main() {
68     int n, m, s, t; scanf("%d%d%d%d",&n,&m,&s,&t);
69     mcmf.init(n);
70     for (int i = 1; i <= m; ++i) {
71         int u, v, w, f; scanf("%d%d%d%d",&u,&v,&w,&f);
72         mcmf.AddEdge(u,v,w,f);
73     }
74     pair<int,int> ans = mcmf.mincost(s,t);
75     printf("%d %d\n",ans.first,ans.second);
76     return 0;
77 }

标签：int,flow,最小,edges,cost,que,P3381,maxn,模板
来源： https://www.cnblogs.com/wstong/p/11781519.html