luogu3386 【模板】二分图匹配 匈牙利算法 hdu2063 过山车 dinic

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;
}