二分图匹配

 1 /*
 2   题意：二分图匹配
 3   题解：
 4   时间：2018.07.18
 5 */
 6 
 7 #include <bits/stdc++.h>
 8 using namespace std;
 9 
10 typedef long long LL;
11 const int MAXN = 100005;
12 const LL MOD7 = 1e9+7;
13 
14 struct Edge
15 {
16     int u,v;
17     int next;
18 }edge[2*MAXN];
19 
20 int head[MAXN];
21 int cnt;
22 
23 int mark[MAXN];
24 int n,m;
25 int vis[MAXN];
26 
27 void init()
28 {
29     cnt=0;
30     memset(head,-1,sizeof(head));
31 }
32 
33 void addEdge(int u,int v)
34 {
35     edge[cnt].u=u;edge[cnt].v=v;edge[cnt].next=head[u];head[u]=cnt++;
36 }
37 
38 bool dfs(int u)
39 {
40     for (int i=head[u];i!=-1;i=edge[i].next)
41     {
42         int v=edge[i].v;
43         if (vis[v]) continue;
44         vis[v]=1;
45         if (mark[v]==-1 || dfs(mark[v]))
46         {
47             mark[v]=u;
48             return true;
49         }
50     }
51     return false;
52 }
53 
54 void work()
55 {
56     int ans=0;
57     memset(mark,-1,sizeof(mark));
58     for (int i=1;i<=n;++i)
59     {
60         memset(vis,0,sizeof(vis));
61         ans+=dfs(i);
62     }
63     printf("%d\n",ans/2);
64 }
65 
66 int main()
67 {
68 #ifndef ONLINE_JUDGE
69     freopen("test.txt","r",stdin);
70 #endif // ONLINE_JUDGE
71     scanf("%d%d",&n,&m);
72     int u,v;
73     init();
74     for (int i=1;i<=m;++i)
75     {
76         scanf("%d%d",&u,&v);
77         addEdge(u,v);
78         addEdge(v,u);
79     }
80     work();
81     return 0;
82 }