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
", ans);
}
return 0;
}