luogu2756 飞行员配对方案问题

匈牙利

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
int n, m, lst[105], uu, vv, cnt, ans;
bool edge[105][105], vis[105];
bool dfs(int x){
	for(int i=m+1; i<=n; i++)
		if(edge[x][i] && !vis[i]){
			vis[i] = true;
			if(!lst[i] || dfs(lst[i])){
				lst[i] = x;
				return true;
			}
		}
	return false;
}
int main(){
	cin>>m>>n;
	while(scanf("%d %d", &uu, &vv)!=EOF && uu>0)
		edge[uu][vv] = true;
	for(int i=1; i<=m; i++){
		memset(vis, 0, sizeof(vis));
		if(dfs(i))	ans++;
	}
	if(!ans)	cout<<"No Solution!"<<endl;
	else cout<<ans<<endl;
	for(int i=m+1; i<=n; i++)
		if(lst[i])
			printf("%d %d\n", lst[i], i);
	return 0;
}

dinic

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
struct Edge{
	int too, nxt, val;
}edge[10005];
int m, n, hea[105], uu, vv, cnt, lev[105], ss, tt, maxFlow;
const int oo=0x3f3f3f3f;
bool a[105][105];
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++;
}
void addEdge(int fro, int too, int val){
	add_edge(fro, too, val);
	add_edge(too, fro, 0);
}
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(){
	memset(hea, -1, sizeof(hea));
	cin>>m>>n;
	ss = 0; tt = n + 1;
	while(scanf("%d %d", &uu, &vv)!=EOF && uu>0)
		a[uu][vv] = true;
	for(int i=1; i<=m; i++){
		addEdge(ss, i, 1);
		for(int j=m+1; j<=n; j++)
			if(a[i][j])
				addEdge(i, j, 1);
	}
	for(int i=m+1; i<=n; i++)
		addEdge(i, tt, 1);
	dinic();
	if(!maxFlow)	cout<<"No Solution!\n";
	else cout<<maxFlow<<endl;
	for(int i=1; i<=m; i++)
		for(int j=hea[i]; j!=-1; j=edge[j].nxt)
			if(edge[j^1].val && edge[j].too)
				printf("%d %d\n", i, edge[j].too);
	return 0;
}