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| #include <cstdio>
#include <queue>
#include <cstring>
const int maxn = 12005;
const int INF = 0x3f3f3f3f;
using namespace std;
struct E{
int to, nxt, f;
}e[maxn << 1];
int head[maxn], tot = 1;
void addedge(int u, int v, int f){
e[++tot].to = v, e[tot].nxt = head[u], e[tot].f = f;
head[u] = tot;
}
void ins(int u, int v, int f){
addedge(u, v, f);
addedge(v, u, 0);
}
int dep[maxn], now[maxn], T;
bool bfs(){
queue <int> q; while (!q.empty()) q.pop();
q.push(0); memset(dep, 0, sizeof dep); dep[0] = 1;
memcpy(now, head, sizeof now);
while (!q.empty()){
int cur = q.front(); q.pop();
for (int i = head[cur]; i; i = e[i].nxt)
if (!dep[e[i].to] && e[i].f){
dep[e[i].to] = dep[cur] + 1;
q.push(e[i].to);
}
}
return dep[T];
}
int upper[maxn];
int dfs(int cur, int Max){
if (cur == T) return Max;
int flow = 0;
for (int i = now[cur]; i; i = e[i].nxt){
now[cur] = i;
if (flow >= Max) return flow;
if (dep[e[i].to] == dep[cur] + 1 && e[i].f){
int tmp = dfs(e[i].to, min(Max - flow, e[i].f));
if (tmp == 0) continue;
e[i].f -= tmp;
e[i ^ 1].f += tmp;
flow += tmp;
}
}
return flow;
}
int maxflow = 0;
void Dinic(){
while (bfs())
maxflow += dfs(0, INF);
}
int n, m, res[maxn], last[maxn];
bool vis[maxn];
int main(){
scanf("%d%d", &n, &m);
for (int u, v, i = 1; i <= m; i++){
scanf("%d%d", &u, &v);
ins(u << 1, v << 1 | 1, 1);
} T = n * 2 + 2;
for (int i = 1; i <= n; i++) ins(0, i << 1, 1), ins(i << 1 | 1, T, 1), last[i] = tot - 1;
Dinic();
int ans = n - maxflow;
for (int i = 1; i <= n; i++){
if (vis[i] || e[last[i]].f == 0) continue;
int cur = i << 1;
while (1){
vis[cur >> 1] = 1; bool f = 0; printf("%d ", cur >> 1);
for (int j = head[cur]; j; j = e[j].nxt)
if (e[j].f == 0 && e[j].to != 0) f = 1, cur = e[j].to - 1;
if (!f) break;
} puts("");
}
printf("%d\n", ans);
return 0;
}
|