Kosaraju algorithm || Find strongly connected component

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 100005;

int n,m,tplt=0;
vector<vector<int>> a,b;
stack<int> s;
vector<bool> visited;
vector<int> res[N];

void dfs1(int u)
{
    visited[u]=true;
    for(int i = 0; i<a[u].size(); ++i)
    {
        if (!visited[a[u][i]]) {
            dfs1(a[u][i]);
        }
    }
    s.push(u);
}

void dfs2(int u, int d)
{
    visited[u]=true;
    for(int i = 0; i<b[u].size(); ++i)
    {
        int v = b[u][i];
        if (!visited[v])
        {
            res[d].push_back(v);
            dfs2(v,d);
        }
    }
}

void sol()
{
    for(int i=1; i<=n; ++i) if(!visited[i]) dfs1(i);
    for(int i=1; i<=n; ++i) visited[i]=false;
    while (!s.empty())
    {
        int z = s.top(); s.pop();
        if (!visited[z])
        {
            ++tplt;
            res[tplt].push_back(z);
            dfs2(z,tplt);
        }
    }
    cout << tplt << endl;
    for(int i=1; i<=tplt; ++i)
    {
        cout << res[i].size() << endl;
        for(int v : res[i])
        {
            cout << v << " ";
        }
        cout << endl;
    }
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    //freopen("sconnect.inp","r",stdin);
    cin >> n >> m;
    a.resize(n+1,vector<int>(0));
    b.resize(n+1,vector<int>(0));
    visited.resize(n+1,false);
    for(int i=1; i<=m; ++i)
    {
        int u,v;
        cin >> u >> v;
        a[u].push_back(v);
        b[v].push_back(u);
    }
    sol();
    return 0;
}