Straw Millionaire

    1#include <bits/stdc++.h>
    2using namespace std;
    3using ll = long long;
    4using i128 = __int128;
    5const int inf = 1e9;
    6const ll INF = 2e18; //❄️
    7int main() {
    8    ios::sync_with_stdio(0); cin.tie(0); 
    9    int n, m; cin >> n >> m;
    10    vector<vector<int>> adj(n + 1);
    11    for (int i = 0; i < m; i++) {
    12        int u, v; cin >> u >> v;
    13        adj[u].push_back(v);
    14    }
    15    int cnt = 0;
    16    vector<int> vis(n + 1);
    17    auto dfs = [&](auto &&self, int x) -> void {
    18        if (vis[x]) return;
    19        vis[x] = 1;
    20        for (int v : adj[x]) {
    21            self(self, v);
    22        }
    23        return;
    24    };
    25    dfs(dfs, 1);
    26    for (int i = 1; i < vis.size(); i++) {
    27        if (vis[i]) cnt++;
    28    }
    29    cout << cnt << '\n';
    30    return 0;
    31}