P1726 上白泽慧音 - 强连通分量模板

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/Fantasy_World/article/details/82932293

虽然是模板但是却提醒我有向图一定要试着从每个点出发，不仅仅是因为图不一定连通，更有可能是只从1号点出发哪也去不了的情况

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <stack>
using namespace std;
#define debug(x) cerr << #x << "=" << x << endl;
const int MAXN = 10000 + 10;
stack<int> s;
int n,m,vis[MAXN],last[MAXN],edge_tot,temp[MAXN],fina[MAXN],ans,dfn[MAXN],low[MAXN],flg[MAXN],cnt;
struct Edge{
	int u, v, w, to;
	Edge(){}
	Edge(int u, int v, int to) : u(u), v(v), to(to) {}
}e[50001 * 2];
inline void add(int u, int v) {
	e[++edge_tot] = Edge(u, v, last[u]);
	last[u] = edge_tot; 
}
bool cmp(int a, int b) {
	return a < b;
}
void tarjan(int x) {
	dfn[x] = low[x] = ++cnt;
	s.push(x);
	flg[x] = true;
	for(int i=last[x]; i; i=e[i].to) {
		int v = e[i].v;
		if(!dfn[v]) {
			tarjan(v);
			if(low[v] < low[x]) low[x] = low[v];
		} else if(dfn[v] < low[x] && flg[v]) {
			low[x] = dfn[v];
		}
	}
	if(dfn[x] == low[x]) {
		int j, num=0;
		do{
			j = s.top();
			s.pop();
			temp[++num] = j; 
			flg[j] = 0;
		}while(j != x);
		sort(temp+1, temp+num+1, cmp);
		if(num > ans) {
			memcpy(fina, temp, sizeof(temp));
			ans = num;
		} else if(num == ans) {
			if(memcmp(fina, temp, sizeof(temp)) > 0) 
				memcpy(fina, temp, sizeof(temp));
		}
	}
	
}
int main() {
	scanf("%d%d", &n, &m);
	for(int i=1; i<=m; i++) {
		int a,b,t;
		scanf("%d%d%d",&a, &b, &t);
		add(a, b);
		if(t == 2) add (b, a);
	}
	for(int i=1; i<=n; i++) 
		if(!dfn[i]) //关键之处
			tarjan(i);
	printf("%d\n", ans);
	for(int i=1; i<=ans; i++) {
		printf("%d ", fina[i]);
	}
	return 0;
}