桥和割点的tarjan算法

–桥和割点的tarjan算法

前言

最近学习了这个算法，感觉很神奇

代码如下（示例）：

在这里插入代码片
#include<iostream>
using namespace std;
#include<map>
#include<vector>
const int maxn = 1e6 + 5;
vector<int> son[maxn];
int fa[maxn], dfn[maxn], low[maxn];
int iscp[maxn], isce[maxn];
map<int, int> mp[maxn];
int cnt = 0;
int root;
void dfs(int u) {
	dfn[u] = ++cnt;
	low[u] = cnt;
	for (int i = 0; i < son[u].size(); i++) {
		int v = son[u][i];
		if (!dfn[v]) {
			fa[v] = u;
			dfs(v);
			low[u] = min(low[u], low[v]);
			if (dfn[u] <= low[v] && u != root) {
				iscp[u] = 1;
			}
			if (dfn[u] < low[v] && mp[u][v] <= 1 && mp[v][u] <= 1) {
				isce[v] = 1;
			}
		} else if ( v != fa[u])  low[u] = min(low[u], dfn[v]);
	}
}
int main() {
	int n, m;
	cin >> n >> m;
	for (int i = 1; i <= m; i++) {
		int u, v;
		cin >> u >> v;
		son[u].push_back(v);
		son[v].push_back(u);
		if (u > v) {
			mp[u][v]++;
		}
	}
	for (int i = 1; i <= n; i++) {
		int t = 0;
		if (!dfn[i]) {
			root = i;
			dfs(i);
			for (int j = 0; j < son[i].size(); j++) {
				int v = son[i][j];
				if (fa[v] == i) {
					t++;
				}
			}
			if (t > 1) {
				iscp[i] = 1;
			}
		}
	}
	for(int i=1;i<=n;i++){
		if(iscp[i]){
			cout << i <<" ";
		}
	}
	cout << endl;
	for(int i=1;i<=n;i++){
		if(isce[i]){
			cout << '(' << i <<','<<fa[i]<<')'<<"     ";
		}
	}
}