【luogu P2071 座位安排】 题解

题目链接：https://www.luogu.org/problemnew/show/P2071#sub

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：

 #include <iostream>
 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 using namespace std;
 inline int read()
 {
     int ret=;
     char c=getchar();
     while (c<'' || c>'') c=getchar();
     while (c>='' && c<=''){
         ret=((ret<<)+(ret<<))+c-'';
         c=getchar();
     }
     return ret;
 }
 const int maxn = ;
 int n, ans, cnt;
 int link[maxn], head[maxn];
 bool vis[maxn];
 struct edge{
     int v,next;
 }e[maxn<<];
 void add(int u, int v)
 {
     e[++cnt].v = v;
     e[cnt].next = head[u];
     head[u] = cnt;
 }
 bool dfs(int u)
 {
     int v = head[u];
     for(int i = v; i != ; i = e[i].next)
     {
         if(!vis[e[i].v])
         {
             vis[e[i].v] = ;
             if(!link[e[i].v] || dfs(link[e[i].v]))
             {
                 link[e[i].v] = u;
                 return ;
             }
         }
     }
     return ;
 }
 int main()
 {
     int u,v;
     n = read();
     for(int i = ; i <= n*; i++)
     {
         u = read(); v = read();
         add(i,u);
         add(i,u+n);
         add(i,v);
         add(i,v+n);
     }
     for(int i = ; i <= n*; i++)
     {
         memset(vis,,sizeof(vis));
         if(dfs(i)) ans++;
     }
     printf("%d",ans);
     return ;
 }