HDU2063_过山车_C++

　　题目：http://acm.hdu.edu.cn/showproblem.php?pid=2063

　　又是一道二分图匹配的裸题，直接上匈牙利算法

　　注意一点它末尾的0结束，是标志着有多组数据……坑……

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<ctime>
#include<queue>
#define fre(x) freopen(x".in","r",stdin);freopen(x".out","w",stdout)
#define Test1 freopen("in.in","r",stdin);freopen("1.out","w",stdout)
#define Test2 freopen("in.in","r",stdin);freopen("2.out","w",stdout)
using namespace std;
typedef long long LL;
typedef double db;
const double CPS=CLOCKS_PER_SEC,TL=0.98;
const int oo=2147483647,N=501,M=1001;
int first[N],Next[M],v[M],g[N];
bool f[N];
inline bool xyl(int x)
{
    int i,k;
    for (i=first[x];i;i=Next[i])
    {
        k=v[i];
        if (f[k])
        {
            f[k]=0;
            if ((!g[k])||xyl(g[k]))
            {
                g[k]=x;
                return 1;
            }
        }
    }
    return 0;
}
int main()
{
    int n,na,nb,i,j,ans,x;
    scanf("%d",&n);
    while (n)
    {
        ans=0;
        scanf("%d%d",&na,&nb);
        for (i=1;i<=na;i++) first[i]=0;
        for (i=1;i<=nb;i++) g[i]=0;
        for (i=1;i<=n;i++)
        {
            scanf("%d%d",&x,&v[i]);
            Next[i]=first[x];
            first[x]=i;
        }
        for (i=1;i<=na;i++)
        {
            for (j=1;j<=nb;j++) f[j]=1;
            if (xyl(i)) ans++;
        }
        printf("%d
",ans);
        scanf("%d",&n);
    }
    return 0;
} 

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