匈牙利算法dfs模板 [二分图][二分图最大匹配]

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 using namespace std;
 5 
 6 struct Edge{
 7     int to,nxt;
 8     Edge(int to=0,int nxt=0):
 9         to(to),nxt(nxt){}
10 };
11 
12 const int maxn=2005,maxm=1000005;
13 
14 Edge E[maxm<<1];
15 int head[maxn],mat[maxn];
16 bool check[maxn];
17 int n,n_l,n_r,m,cnt=0;
18 
19 bool dfs(int u){
20     for(int e=head[u];e;e=E[e].nxt){
21         int v=E[e].to;
22         if(!check[v]){
23             check[v]=1;
24             if(mat[v]==-1||dfs(mat[v])){
25                 mat[v]=u;
26                 mat[u]=v;
27                 return 1;
28             }
29         }
30     }
31     return 0;
32 }
33 
34 void hungarian(){
35     int ans=0;
36     memset(mat,-1,sizeof mat);
37     for(int u=1;u<=n_l;u++)
38         if(mat[u]==-1){
39             memset(check,0,sizeof check);
40             if(dfs(u))  ans++;
41         }
42     printf("%d\n",ans);
43 }
44 
45 inline void ad_e(int from=0,int to=0){
46     E[++cnt]=Edge(to,head[from]);
47     head[from]=cnt;
48     E[++cnt]=Edge(from,head[to]);
49     head[to]=cnt;
50 }
51 
52 void init(){
53     scanf("%d%d%d",&n_l,&n_r,&m);
54     for(int i=0,ff,tt;i<m;i++){
55         scanf("%d%d",&ff,&tt);
56         if(tt>n_r)  continue;
57         ad_e(ff,tt+n_l);
58     }
59 }
60 
61 int main(){
62     init();
63     hungarian();
64     return 0;
65 }