hdu 2444 The Accomodation of Students

#include <cstring>
#include <cstdio>
#include <vector>
#include <queue>
#define N 300
using namespace std;
vector<int>G[N];
bool vis[N],flag;
int Map[N][N],match[N],col[N],cnt,n,m;
int dfs(int x)
{
    for(int i=1;i<=n;++i)
    {
        if(Map[x][i]&&!vis[i])
        {
            vis[i]=1;
            if(!match[i]||dfs(match[i]))
            {
                match[i]=x;
                return 1;
            }
        }
    }
    return 0;
}
bool rs(int x)
{
    queue<int>q;
    q.push(x);
    col[x]=0;
    for(int now;!q.empty();)
    {
        now=q.front();
        q.pop();
        for(int i=0;i<G[now].size();++i)
        {
            int v=G[now][i];
            if(col[v]!=-1) {if(col[now]==col[v]) {flag=1;return true;}}
            else
            {
                col[v]=col[now]^1;
                q.push(v); 
            }
        }
    }
    return false;
}
int main()
{
    for(int last=0;scanf("%d%d",&n,&m)!=EOF;last=n)
    {
        for(int i=1;i<=last;++i) G[i].clear();
        int ans=0;
        flag=false;
        memset(Map,0,sizeof(Map));
        memset(col,-1,sizeof(col));
        memset(match,0,sizeof(match));
        for(int x,y;m--;)
        {
            scanf("%d%d",&x,&y);
            Map[x][y]=1;
            G[x].push_back(y);
            G[y].push_back(x);  
        }
        for(int i=1;i<=n;++i) if(col[i]==-1) if(rs(i)) break;
        if(flag) {printf("No\n");continue;}
        for(int i=1;i<=n;++i)
        {
            memset(vis,0,sizeof(vis));
            ans+=dfs(i);
        }
        printf("%d\n",ans);
    }
    return 0;
}