POJ 3041 Asteroids

 

同Hdu 2119 Matrix.

CODE：

 

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;

#define MAXN 510
#define MAXM 10010

struct Edge
{
    int v, next;
}edge[MAXM];

int n, m;
int cnt;

int first[MAXN], link[MAXN];
bool vis[MAXN];

void init()
{
    cnt = 0;
    memset(first, -1, sizeof(first));
    memset(link, -1, sizeof(link));
}

void read_graph(int u, int v)
{
    edge[cnt].v = v;
    edge[cnt].next = first[u]; first[u] = cnt++;
}

void read_graph2()
{
    while(m--)
    {
        int u, v;
        scanf("%d%d", &u, &v);
        read_graph(u, v);
    }
}

int ED(int u)
{
    for(int e = first[u]; e != -1; e = edge[e].next)
    {
        int v = edge[e].v;
        if(!vis[v])
        {
            vis[v] = true;
            if(link[v] == -1 || ED(link[v]))
            {
                link[v] = u;
                return true;
            }
        }
    }
    return false;
}

void solve()
{
    int ans = 0;
    for(int i = 1; i <= n; i++)
    {
        memset(vis, false, sizeof(vis));
        if(ED(i)) ans++;
    }
    printf("%d\n", ans);
}

int main()
{
    while(~scanf("%d%d", &n, &m))
    {
        init();
        read_graph2();
        solve();
    }
    return 0;
}