luogu

匈牙利算法

#include <iostream>

#include <cstring>

#include <cstdio>

using namespace std;

int n, m, uu, vv, e, lnk[1005], ans;

bool a[1005][1005], vis[1005];

bool dfs(int u){

	for(int i=1; i<=m; i++){

		if(a[u][i] && !vis[i]){

			vis[i] = true;

			if(!lnk[i] || dfs(lnk[i])){

				lnk[i] = u;

				return true;

			}

		}

	}

	return false;

}

int main(){

	cin>>n>>m>>e;

	for(int i=1; i<=e; i++){

		scanf("%d %d", &uu, &vv);

		if(uu>n || vv>m)	continue;

		a[uu][vv] = true;

	}

	for(int i=1; i<=n; i++){

		memset(vis, 0, sizeof(vis));

		if(dfs(i))	ans++;

	}

	cout<<ans<<endl;

	return 0;

}

hdu

建图最大流dinic

#include <iostream>

#include <cstring>

#include <cstdio>

#include <queue>

using namespace std;

struct Edge{

	int too, nxt, val;

}edge[4005];

int k, m, n, ss, tt, cnt, hea[1005], uu, vv, maxFlow, lev[1005];

const int oo=0x3f3f3f3f;

queue<int> d;

void add_edge(int fro, int too, int val){

	edge[cnt].nxt = hea[fro];

	edge[cnt].too = too;

	edge[cnt].val = val;

	hea[fro] = cnt++;

}

bool bfs(){

	memset(lev, 0, sizeof(lev));

	d.push(ss);

	lev[ss] = 1;

	while(!d.empty()){

		int x=d.front();

		d.pop();

		for(int i=hea[x]; i!=-1; i=edge[i].nxt){

			int t=edge[i].too;

			if(!lev[t] && edge[i].val>0){

				lev[t] = lev[x] + 1;

				d.push(t);

			}

		}

	}

	return lev[tt]!=0;

}

int dfs(int x, int lim){

	if(x==tt)	return lim;

	int addFlow=0;

	for(int i=hea[x]; i!=-1 && addFlow<lim; i=edge[i].nxt){

		int t=edge[i].too;

		if(lev[t]==lev[x]+1 && edge[i].val>0){

			int tmp=dfs(t, min(lim-addFlow, edge[i].val));

			edge[i].val -= tmp;

			edge[i^1].val += tmp;

			addFlow += tmp;

		}

	}

	return addFlow;

}

void dinic(){

	while(bfs())	maxFlow += dfs(ss, oo);

}

int main(){

	while(scanf("%d", &k)!=EOF){

		if(!k)	break;

		scanf("%d %d", &m, &n);

		ss = 0; tt = m + n + 1;

		memset(hea, -1, sizeof(hea));

		cnt = maxFlow = 0;

		for(int i=1; i<=k; i++){

			scanf("%d %d", &uu, &vv);

			add_edge(uu, vv+m, 1);

			add_edge(vv+m, uu, 0);

		}

		for(int i=1; i<=m; i++){

			add_edge(ss, i, 1);

			add_edge(i, ss, 0);

		}

		for(int i=m+1; i<=m+n; i++){

			add_edge(i, tt, 1);

			add_edge(tt, i, 0);

		}

		dinic();

		printf("%d\n", maxFlow);

	}

	return 0;

}