bzoj1854

 1 #include<bits/stdc++.h>
 2 #define lowbit(a) ((a)&(-(a)))
 3 #define clr(a,x) memset(a,x,sizeof(a))
 4 #define rep(i,l,r) for(int i=l;i<(r);i++)
 5 typedef long long ll;
 6 using namespace std;
 7 int read()
 8 {
 9     char c=getchar();
10     int ans=0,f=1;
11     while(!isdigit(c)){
12         if(c==‘-‘) f=-1;
13         c=getchar();
14     }
15     while(isdigit(c)){
16         ans=ans*10+c-‘0‘;
17         c=getchar();
18     }
19     return ans*f;
20 }
21 const int maxn=1000009,maxk=10009;
22 int n,ans,match[maxn+maxk],vis[maxn+maxk];
23 vector<int>e[maxn+maxk];
24 void addedge(int u,int v){
25     e[u].push_back(v);
26     e[v].push_back(u);
27 }
28 bool dfs(int k){
29     rep(i,0,e[k].size()){
30         int v=e[k][i];
31         if(vis[v]!=ans){
32             vis[v]=ans;
33             if(!match[v]||dfs(match[v])){
34                 match[v]=k;
35                 return 1;
36             } 
37         }
38     }
39     return 0;
40 }
41 int main()
42 {    
43     n=read();
44     rep(i,1,n+1){
45         int u=read(),v=read();
46         addedge(u,i+10000);addedge(v,i+10000);
47     }
48     int sum=0;
49     for(ans=1;ans<=10000;ans++){
50         if(dfs(ans)) ++sum;
51         else break;
52     }
53     printf("%d\n",sum);
54     return 0;
55 }