P3916 图的遍历

题面：
链接：https://www.luogu.com.cn/problem/P3916
思路：反向遍历图

啊卡了好久，如果正序来的话还得考虑环和先后次序的问题
代码：

#include<iostream>
#include<vector>
#include<algorithm>
#include<math.h>
#include<sstream>
#include<string>
#include<string.h>
#include<iomanip>
#include<stdlib.h>
#include<map>
#include<queue>
#include<cmath>
#include<limits.h>
#include<climits>
#include<fstream>
#include<stack>
#include<set>
typedef long long ll;
using namespace std;

const int N = 1e5 + 10;
vector<int>tonxt[N];
int maxn[N];
bool vis[N];
bool visbegin[N];
void dfs(int i,int goal)
{
	if (vis[i])return;
	vis[i] = true;
	maxn[i] = goal;
	for (int k = 0; k < tonxt[i].size(); k++)
	{
		dfs(tonxt[i][k], goal);
	}
	return;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
	int n, m; cin >> n >> m;
	for (int i = 0; i < m; i++)
	{
		int from, to;
		cin >> from >> to;
		tonxt[to].push_back(from);
	}
	for (int i = n; i >= 1; i--)
		dfs(i,i);
	for (int i = 1; i <= n; i++)cout << maxn[i] << ' ';
	return 0;
}