【费用流】bzoj1877: [SDOI2009]晨跑

 1 #include<bits/stdc++.h>
 2 const int maxn = 503;
 3 const int maxm = 50035;
 4 const int INF = 2e9;
 5 
 6 struct Edge
 7 {
 8     int u,v,f,c,cst;
 9     Edge(int a=0, int b=0, int c=0, int d=0, int e=0):u(a),v(b),f(c),c(d),cst(e) {}
10 }edges[maxm];
11 int n,m,S,T;
12 bool inq[maxn];
13 int bck[maxn],cst[maxn],flw[maxn];
14 int edgeTot,head[maxn],nxt[maxm];
15 
16 int read()
17 {
18     char ch = getchar();
19     int num = 0, fl = 1;
20     for (; !isdigit(ch); ch=getchar())
21         if (ch==‘-‘) fl = -1;
22     for (; isdigit(ch); ch=getchar())
23         num = (num<<1)+(num<<3)+ch-48;
24     return num*fl;
25 }
26 void addedge(int u, int v, int cap, int cst)
27 {
28     edges[edgeTot] = Edge(u, v, 0, cap, cst), nxt[edgeTot] = head[u], head[u] = edgeTot++;
29     edges[edgeTot] = Edge(v, u, 0,  0, -cst), nxt[edgeTot] = head[v], head[v] = edgeTot++;
30 }
31 void maxFlow()
32 {
33     int mxFlw = 0, cost = 0;
34     for (;;)
35     {
36         std::queue<int> q;
37         memset(flw, 0, sizeof flw);
38         memset(bck, 0, sizeof bck);
39         memset(cst, 0x3f3f3f3f, sizeof cst);
40         q.push(S), flw[S] = INF, cst[S] = 0;
41         for (int tmp; q.size(); )
42         {
43             tmp = q.front(), q.pop(), inq[tmp] = 0;
44             for (int i=head[tmp]; i!=-1; i=nxt[i])
45             {
46                 int v = edges[i].v;
47                 if (cst[tmp]+edges[i].cst < cst[v]&&edges[i].f < edges[i].c){
48                     bck[v] = i, cst[v] = cst[tmp]+edges[i].cst;
49                     flw[v] = std::min(flw[tmp], edges[i].c-edges[i].f);
50                     if (!inq[v]) inq[v] = 1, q.push(v);
51                 }
52             }
53         }
54         if (!flw[T]) break;
55         for (int i=T; i!=S; i=edges[bck[i]].u)
56             edges[bck[i]].f += flw[T], edges[bck[i]^1].f -= flw[T];
57         mxFlw += flw[T], cost += cst[T]*flw[T];
58     }
59     printf("%d %d\n",mxFlw,cost);
60 }
61 int main()
62 {
63     memset(head, -1, sizeof head);
64     n = read(), m = read(), S = 0, T = 2*n+2;
65     for (int i=1; i<=m; i++)
66     {
67         int u = read(), v = read(), cst = read();
68         addedge(u+n, v, 1, cst);
69     }
70     for (int i=1; i<n; i++) addedge(i, i+n, 1, 0);
71     addedge(S, n+1, INF, 0), addedge(n, T, INF, 0);
72     maxFlow();
73     return 0;
74 }