HDU 1151 - Air Raid

Posted 2020-07-08 nicetomeetu

很明显求最小路径覆盖

就是求最大匹配

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <vector>
 5 using namespace std;
 6 const int maxn=200;
 7 vector<int> map[maxn];
 8 int vis[maxn];
 9 int link[maxn];
10 int n,k;
11 bool dfs(int t)
12 {
13     int i,x,size=map[t].size();
14     for(i=0;i<size;++i)
15     {
16         x=map[t][i];
17         if(!vis[x])
18         {
19             vis[x]=1;
20             if(link[x]==-1||dfs(link[x]))
21             {
22                 link[x]=t;
23                 return 1;
24             }
25         }
26     }
27     return 0;
28 }
29 int main()
30 {
31     int i,a,b,ans,t;
32     scanf("%d",&t);
33     while(t--)
34     {
35         scanf("%d%d",&n,&k);
36         for(i=1;i<=n;++i) map[i].clear();
37         for(i=1;i<=k;++i)
38         {
39             scanf("%d%d",&a,&b);
40             map[a].push_back(b);
41         }
42         memset(link,-1,sizeof(link));
43         ans=0;
44         for(i=1;i<=n;++i)
45         {
46             memset(vis,0,sizeof(vis));
47             if(dfs(i)) ans++;
48         }
49         printf("%d\n",n-ans);
50     }
51 }