题目链接：

邻接表 + 匈牙利

把之前的邻接矩阵匈牙利变成邻接表

要不然存不下...

code：

1 #include 
     
       2 #include 
      
        3 #include 
       
         4 #include 
        
          5 using namespace std; 6 inline int read() 7 { 8     int ret=0; 9     char c=getchar();10     while (c<'0' || c>'9') c=getchar();11     while (c>='0' && c<='9'){12         ret=((ret<<3)+(ret<<1))+c-'0';13         c=getchar();14     }15     return ret;16 }17 const int maxn = 4010;18 int n, ans, cnt;19 int link[maxn], head[maxn];20 bool vis[maxn];21 struct edge{22     int v,next;23 }e[maxn<<2];24 void add(int u, int v)25 {26     e[++cnt].v = v;27     e[cnt].next = head[u];28     head[u] = cnt;29 }30 bool dfs(int u)31 {32     int v = head[u];33     for(int i = v; i != 0; i = e[i].next)34     {35         if(!vis[e[i].v])36         {37             vis[e[i].v] = 1;38             if(!link[e[i].v] || dfs(link[e[i].v])) 39             {40                 link[e[i].v] = u;41                 return 1;42             }43         }    44     }45     return 0;46 }47 int main()48 {49     int u,v;50     n = read();51     for(int i = 1; i <= n*2; i++)52     {53         u = read(); v = read();54         add(i,u);55         add(i,u+n);56         add(i,v);57         add(i,v+n);58     }59     for(int i = 1; i <= n*2; i++)60     {61         memset(vis,0,sizeof(vis));62         if(dfs(i)) ans++;63     }64     printf("%d",ans);65     return 0; 66 }