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| #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> P;
#define ms(a, b) memset((a), (b), sizeof(a))
const int N = (int)1e5 + 5;
const int INF = 0x3f3f3f3f;
inline int read() {
int res = 0;bool f = 0;char ch = getchar();
while (ch < '0' || ch > '9') { if (ch == '-') f = 1; ch = getchar(); }
while (ch <= '9' && ch >= '0') { res = (res << 3) + (res << 1) + ch - '0'; ch = getchar(); }
return f ? (~ res + 1) : res;
}
struct edge{
int u, v, ne;
}ed[N];
int head[N], dis[N], vis[N], cnt, n, m, tot;
int dfn[N], low[N];
int s[N], ind;
inline void init(){
ms(head, -1);
ms(dis, INF);
ms(vis, 0);
ind = tot = cnt = 0;
}
inline void add(int u, int v){
ed[cnt] = {u, v, head[u]};
head[u] = cnt++;
}
void tarjan(int x){
dfn[x] = low[x] = ++tot;
s[++ind] = x;
vis[x] = 1;
for (int i = head[x]; ~i; i = ed[i].ne){
int v = ed[i].v;
if (!dfn[v]){
tarjan(v); low[x] = min(low[x], low[v]);
}
else if (vis[v]){
low[x] = min(low[x], dfn[v]);
}
}
if (low[x] == dfn[x]){
do {
printf("%d ", s[ind]);
vis[s[ind]] = 0;
ind--;
}while(x != s[ind + 1]);
printf("\n");
}
}
int main(){
init();
scanf("%d%d", &n, &m);
int u, v;
for (int i = 1; i <= m; ++i){
scanf("%d%d", &u, &v);
add(u, v);
}
for (int i = 1; i <= n; ++i){
if (!dfn[i]) tarjan(i);
}
return 0;
}
|