hdu-1068&&POJ1466 Girls and Boys---the largest indie set

Topic link:

http://acm.hdu.edu.cn/showproblem.php?pid=1068

Topic meaning:

There are n people, some people know other people, choose a set so that everyone in the set does not know each other, find the maximum number of people in the set.

Problem solving ideas:

This is the maximum independent set

Maximum independent set = n - minimum number of covers = n - maximum matching

Since xy is mixed here, you can split the points to find the maximum matching, and the final result is twice the real maximum matching

so answer = n - maxmatch() / 2

 

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 const int maxn = 1000 + 10;
 5 const int INF = 1e9;
 6 bool Map[maxn][maxn];
 7 int cx[maxn], cy[maxn];
 8 int cntx, cnty;
 9 bool vis[maxn];
10 bool dfs(int u)
11 {
12     for(intv = 0 v < cnty; v++ )
 13      {
 14          if (Map[u][v] && ! vis[v])
 15          {
 16              vis[v] = 1 ;
17              if (cy[v] == - 1 || dfs(cy[v]))
 18              {
 19                  cx[u] = v;
20                  cy[v] = u;
21                  return  1 ;
22              }
 23          }
 24      }
 25      return  0 ;
26 }
27 int maxmatch()
28 {
29     int ans = 0;
30     memset(cx, -1, sizeof(cx));
31     memset(cy, -1, sizeof(cy));
32     for(int i = 0; i < cntx; i++)
33     {
34         if(cx[i] == -1)
35         {
36             memset(vis, 0, sizeof(vis));
37             ans += dfs(i);
38         }
39     }
40     return ans;
41 }
42 int main()
43 {
44     int n, u, v, t;
45     while(cin >> n)
46     {
47         cntx = cnty = n;
48         memset(Map, 0, sizeof(Map));
49         while(n--)
50         {
51             scanf("%d: (%d)", &u, &t);
52             while(t--)
53             {
54                 scanf("%d", &v);
55                 Map[u][v] = 1;
56             }
57         }
58         int ans = maxmatch();
59         //cout<<ans<<endl;
60         ans = cntx - ans / 2;
61         cout<<ans<<endl;
62     }
63     return 0;
64 }