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scc.cpp
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71 lines (62 loc) · 1.37 KB
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#include <iostream>
#include <cstring>
#include <vector>
#define SIZE 10001
using namespace std;
int V, E;
int scc[SIZE];
int groupNum;
bool visited[SIZE];
vector<int> edge[SIZE], r_edge[SIZE];
vector<int> STACK;
void dfs(int cur) {
visited[cur] = true;
for(int i: edge[cur])
if (!visited[i]) dfs(i);
// 더이상 방문할 정점이 없으면
STACK.push_back(cur); // 깊은 노드부터 스택 푸쉬
}
void r_dfs(int cur, int num) {
visited[cur] = true;
scc[cur] = num; // SCC 번호 부여
for (int i : r_edge[cur])
if (!visited[i]) r_dfs(i, num);
}
void kosaraju(){
/* 순그래프 탐색 (스택 쌓기) */
for(int i = 1; i <= V; i++)
if(!visited[i]) dfs(i);
/* 역그래프 탐색 (SCC 구축)*/
memset(visited, 0, sizeof(visited));
while (!STACK.empty()){
int cur = STACK.back(); STACK.pop_back();
if (visited[cur]) continue;
r_dfs(cur, ++groupNum);
}
/* 출력 */
cout << groupNum << '\n';
for (int i = 1; i <= V; i++) {
if (scc[i] == 0) continue;
cout << i << ' ';
for(int j = i + 1; j <= V; j++)
if (scc[j] == scc[i]) {
cout << j << ' ';
scc[j] = 0;
}
cout << '\n';
}
}
int main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
cin >> V >> E;
int u, v;
for (int i = 0; i < E; i++) {
cin >> u >> v;
edge[u].push_back(v);
r_edge[v].push_back(u);
}
kosaraju();
return 0;
}