poj 3308 Paratroopers 最小割 最小点权覆盖

  1 //#include <bits/stdc++.h>
  2 #include <iostream>
  3 #include <cstring>
  4 #include <cstdio>
  5 #include <cmath>
  6 #include <queue>
  7 #include <vector>
  8 using namespace std;
  9 struct Edge
 10 {
 11     int from, to; double cap, flow;
 12     Edge(int f, int t, double c, double fl)
 13     {
 14         from = f; to = t; cap = c; flow = fl;
 15     }
 16 };
 17 #define maxn 110
 18 #define inf 100000
 19 #define eps 1e-8
 20 int n, m, s, t;
 21 vector <Edge> edges;
 22 vector <int> G[maxn];
 23 int d[maxn], cur[maxn], vis[maxn];
 24 void AddEdge(int from, int to, double cap)
 25 {
 26     edges.push_back(Edge(from, to, cap, 0));
 27     edges.push_back(Edge(to, from, 0, 0));
 28     m = edges.size();
 29     G[from].push_back(m-2);
 30     G[to].push_back(m-1);
 31 }
 32 bool bfs()
 33 {
 34     memset(vis, 0, sizeof(vis));
 35     d[s] = 0; vis[s] = 1;
 36     queue <int> q; q.push(s);
 37     while(!q.empty())
 38     {
 39         int x = q.front(); q.pop();
 40         for(int i = 0; i < G[x].size(); i++)
 41         {
 42             Edge &e = edges[G[x][i]];
 43             if(!vis[e.to] && e.cap > e.flow)
 44             {
 45                 d[e.to] = d[x] + 1;
 46                 vis[e.to] = 1;
 47                 q.push(e.to);
 48             }
 49         }
 50     }
 51     return vis[t];
 52 }
 53 double dfs(int x, double a)
 54 {
 55     if(x == t || fabs(a) < eps) return a;
 56     double flow = 0, f;
 57     for(int &i = cur[x]; i < G[x].size(); i++)
 58     {
 59         Edge &e = edges[G[x][i]];
 60         if(d[e.to] == d[x] + 1 && (f = dfs(e.to, min(a, e.cap - e.flow))) > 0)
 61         {
 62             e.flow += f;
 63             edges[G[x][i]^1].flow -= f;
 64             flow += f;
 65             a -= f;
 66             if(fabs(a) < eps) break;
 67         }
 68     }
 69     return flow;
 70 }
 71 double maxflow()
 72 {
 73     double flow = 0;
 74     while(bfs())
 75     {
 76         memset(cur, 0, sizeof(cur));
 77         flow += dfs(s, inf);
 78     } 
 79     return flow;
 80 }
 81 int T, M, N, L;
 82 int main() 
 83 {
 84     //freopen("in.txt", "r", stdin);
 85     //freopen("out.txt", "w", stdout);
 86     scanf("%d", &T);
 87     while(T--)
 88     {
 89         scanf("%d%d%d",  &M, &N, &L);
 90         edges.clear();
 91         s = 0; t = N+M+1; n = N+M+2;
 92         for(int i = s; i <= t; i++) G[i].clear();
 93         double val;
 94         for(int i = 1; i <= M; i++)
 95         {
 96             scanf("%lf", &val);
 97             AddEdge(s, i, log(val));
 98         }
 99         for(int i = 1; i <= N; i++)
100         {
101             scanf("%lf", &val);
102             AddEdge(i+M, t, log(val));
103         }
104         for(int i = 1; i <= L; i++)
105         {
106             int a, b; scanf("%d%d", &a, &b);
107             AddEdge(a, b+M, inf);
108         }
109         double flow = maxflow();
110         printf("%.4lf\n", exp(flow));
111     }
112     return 0;
113 }