CSES – Planets and Kingdoms

#include<bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define f first
#define s second
#define fastio ios_base::sync_with_stdio(0);cin.tie(0)
using namespace std;
//declare
const int maxn = 1e5+5;
int n,m,color[maxn];
vector<int> G[maxn], reverse_G[maxn], order;
bool vis[maxn], vis2[maxn];
//
void dfs(int cur){
    if(vis[cur]) return;
    vis[cur] = 1;
    for(int adj: G[cur]){
        dfs(adj);
    }
    order.push_back(cur);
}
void dfs2(int cur,int x){
    if(vis2[cur]) return;
    vis2[cur] = 1;
    for(int adj: reverse_G[cur]){
        dfs2(adj,x);
    }
    color[cur] = x;
}
signed main(){
    fastio;
    cin>>n>>m;
    for(int i=0;i<m;i++){
        int a,b; cin>>a>>b;
        G[a].push_back(b);
        reverse_G[b].push_back(a);
    }
    int cnt = 0;
    for(int i=1;i<=n;i++) if(!vis[i]) dfs(i);
    reverse(order.begin(),order.end());
    for(int i:order) if(!vis2[i]) dfs2(i,++cnt);
    cout<<cnt<<"\n";
    for(int i=1;i<=n;i++) cout<<color[i]<<" ";
    cout<<"\n";
    return 0;
}