poj1966 Cable TV Network

拆点。

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
int n, m, hea[2005], cnt, ss, tt, uu, vv, maxFlow, ans, lev[2005];
const int oo=0x3f3f3f3f;
bool w[205][205];
queue<int> d;
struct Edge{
	int too, nxt, val;
}edge[200005];
int p(int x){
	return x;
}
int q(int x){
	return x+n;
}
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));
	lev[q(ss)] = 1;
	d.push(q(ss));
	while(!d.empty()){
		int x=d.front();
		d.pop();
		if(x==p(ss) || x==q(tt))	continue;
		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);
			}
		}
	}
	lev[p(ss)] = lev[q(tt)] = 0;
	return lev[p(tt)]!=0;
}
int dfs(int x, int lim){
	if(x==p(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(){
	maxFlow = 0;
	while(bfs())	maxFlow += dfs(q(ss), oo);
	ans = min(ans, maxFlow);
}
int main(){
	while(scanf("%d %d", &n, &m)!=EOF){
		memset(hea, -1, sizeof(hea));
		memset(w, 0, sizeof(w));
		cnt = 0;
		for(int i=1; i<=m; i++){
			scanf(" (%d,%d)", &uu, &vv);
			uu++; vv++;
			w[uu][vv] = w[vv][uu] = true;
			addEdge(q(uu), p(vv), oo);
			addEdge(q(vv), p(uu), oo);
		}
		for(int i=1; i<=n; i++)
			addEdge(p(i), q(i), 1);
		ans = oo;
		bool flag=false;
		for(int i=1; i<=n; i++)
			for(int j=i+1; j<=n; j++)
				if(!w[i][j]){
					ss = i;
					tt = j;
					flag = true;
					for(int k=1; k<=m; k++){
						edge[2*k-2].val = oo;
						edge[2*k-1].val = 0;
					}
					for(int k=2*m; k<cnt; k++){
						if(k&1)	edge[k].val = 0;
						else	edge[k].val = 1;
					}
					dinic();
				}
		if(!flag)	ans = min(ans, n);
		printf("%d\n", ans);
	}
	return 0;
}