我比较懒，直接用priority_queue写，但是我加了一个找根的操作就 $WA4$，后面我直接改成从 $1$ 搜索就$AC$,为什么嘞？求助！！

代码：

//WA4
#include<bits/stdc++.h>
#define ll long long
#define reg register
using namespace std;
const int maxn=1e5+5;
struct point {
	priority_queue<int,vector<int>,greater<int> >son1;
	priority_queue<int,vector<int>,greater<int> >son2;
} a[maxn];
inline int read() {
	int f=1,x=0;
	char ch=getchar();
	while(ch>'9'||ch<'0') {
		if(ch=='-')f*=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9') {
		x=x*10+ch-'0';
		ch=getchar();
	}
	return x*f;
}
int vis[maxn],In[maxn];
void dfs(int rt) {
	vis[rt]=1;
	printf("%d ",rt);
	while(a[rt].son1.size()) {
		reg int v=a[rt].son1.top();
		a[rt].son1.pop();
		if(!vis[v])dfs(v);
	}
}
void bfs(int rt) {
	memset(vis,0,sizeof(vis));
	queue<int>q;//,vector<int>,greater<int>
	q.push(rt);
	vis[rt]=1;
	while(!q.empty()) {
		int u=q.front();
		q.pop();
		//if(vis[u])continue;
		//vis[u]=1;
		printf("%d ",u);
		while(a[u].son2.size()) {
			reg int v=a[u].son2.top();
			a[u].son2.pop();
			if(!vis[v])q.push(v),vis[v]=1;
		}
	}
}
int main() {
	reg int n=read(),m=read();
	reg int u,v;
	for(reg int i(1); i<=m; ++i) {
		u=read(),v=read();
		a[u].son1.push(v);
		a[u].son2.push(v);
		In[v]++;
	}
	int rt;
	for(reg int i=1; i<=n; ++i) {
		if(!In[i]) {
			rt=i;
			break;
		}
	}
	dfs(rt);
  	//dfs(1);改成这个就AC
	puts("");
	bfs(rt);
  	//bfs(1);改成这个就AC
	return 0;
}