HDU——T 2444 The Accomodation of Students

  1 #include <algorithm>
  2 #include <cstring>
  3 #include <cstdio>
  4 #include <queue>
  5 
  6 using namespace std;
  7 
  8 const int N(233);
  9 int n,m,head[N],sumedge;
 10 struct Edge
 11 {
 12     int v,next;
 13     Edge(int v=0,int next=0):v(v),next(next){}
 14 }edge[233333];
 15 inline void ins(int u,int v)
 16 {
 17     edge[++sumedge]=Edge(v,head[u]);
 18     head[u]=sumedge;
 19     edge[++sumedge]=Edge(u,head[v]);
 20     head[v]=sumedge;
 21 }
 22 
 23 int col[N];
 24 bool Paint(int x)
 25 {
 26     col[x]=0;
 27     queue<int>que;
 28     que.push(x);
 29     for(int u,v;!que.empty();)
 30     {
 31         u=que.front(); que.pop();
 32         for(int i=head[u];i;i=edge[i].next)
 33         {
 34             v=edge[i].v;
 35             if(col[v]!=-1)
 36             {
 37                 if(col[v]==col[u])
 38                     return false;
 39             }
 40             else
 41             {
 42                 col[v]=col[u]^1;
 43                 que.push(v);
 44             }
 45         }
 46     }
 47     return true;
 48 }
 49 
 50 int sumvis,vis[N],match[N],Map[N][N];
 51 bool find(int u)
 52 {
 53     /*for(int v,i=head[i];i;i=edge[i].next)
 54     {
 55         v=edge[i].v;
 56         if(!vis[v])
 57         {
 58             vis[v]=1;
 59             if(!match[v]||find(match[v]))
 60             {
 61                 match[v]=u;
 62                 return true;
 63             }
 64         }
 65     }*/
 66     for(int v=1;v<=n;v++)
 67         if(Map[u][v]&&!vis[v])
 68         {
 69             vis[v]=1;
 70             if(!match[v]||find(match[v]))
 71             {
 72                 match[v]=u;
 73                 return true;
 74             }
 75         }
 76     return false;
 77 }
 78 
 79 inline void init()
 80 {
 81     memset(edge,0,sizeof(edge));
 82     memset(head,0,sizeof(head));
 83     memset(match,0,sizeof(match));
 84 }
 85 
 86 int main()
 87 {
 88     for(;~scanf("%d%d",&n,&m);init())
 89     {
 90         int ans=0,flag=0;sumvis=0;
 91         memset(Map,0,sizeof(Map));
 92         for(int u,v;m--;ins(u,v))
 93             scanf("%d%d",&u,&v),Map[u][v]=1;
 94         memset(col,-1,sizeof(col));
 95         for(int i=1;i<=n;i++)
 96             if(col[i]==-1)
 97                 if(!Paint(i))
 98                 {
 99                     flag=1;
100                     break;
101                 }
102         if(flag)
103         {
104             puts("No");
105             continue;
106         }
107         for(int i=1;i<=n;i++)
108         {
109             if(find(i)) ans++;
110             memset(vis,0,sizeof(vis));
111         }
112         printf("%d\n",ans);
113     }
114     return 0;
115 }