SCC finding problem

Author: koralkulacoglu

CSES/planetsAndKingdoms

@@ -0,0 +1,173 @@
+/*
+ID: Koral Kulacoglu
+TASK: test
+LANG: C++                 
+*/
+
+#include <bits/stdc++.h>
+ 
+using namespace std;
+ 
+typedef long long ll;
+typedef long double ld;
+typedef unsigned long long ull;
+typedef long double lld;
+typedef complex<ld> cd;
+ 
+typedef pair<int, int> pi;
+typedef pair<ll,ll> pll;
+typedef pair<ld,ld> pld;
+ 
+typedef vector<int> vi;
+typedef vector<string> vs;
+typedef vector<char> vc;
+typedef vector<ld> vld;
+typedef vector<ll> vll;
+typedef vector<pi> vpi;
+typedef vector<pll> vpll;
+typedef vector<cd> vcd;
+
+template<class T> using pq = priority_queue<T>;
+template<class T> using pqg = priority_queue<T, vector<T>, greater<T>>;
+ 
+#define FOR(i, a, b) for (int i=a; i<(b); i++)
+#define F0R(i, a) for (int i=0; i<(a); i++)
+#define FORd(i, a, b) for (int i=(a)-1; i >= b; i--)
+#define F0Rd(i, a) for (int i=(a)-1; i >= 0; i--)
+#define trav(a, x) for (auto& a : x)
+#define uid(a, b) uniform_int_distribution<int>(a, b)(rng)
+ 
+#define sz(x) (int)(x).size()
+#define all(x) x.begin(), x.end()
+#define mp make_pair
+#define pb push_back
+#define fir first
+#define sec second
+#define ins insert
+#define lbound(a, v) lower_bound(all(a), v)-a.begin()
+#define ubound(a, v) upper_bound(all(a), v)-a.begin()
+#define gcd(a, b) __gcd(a, b)
+#define lcm(a, b) (a*b)/gcd(a, b)
+ 
+template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
+template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
+
+void __print(int x) {cerr << x;}
+void __print(long x) {cerr << x;}
+void __print(long long x) {cerr << x;}
+void __print(unsigned x) {cerr << x;}
+void __print(unsigned long x) {cerr << x;}
+void __print(unsigned long long x) {cerr << x;}
+void __print(float x) {cerr << x;}
+void __print(double x) {cerr << x;}
+void __print(long double x) {cerr << x;}
+void __print(char x) {cerr << '\'' << x << '\'';}
+void __print(const char *x) {cerr << '\"' << x << '\"';}
+void __print(const string &x) {cerr << '\"' << x << '\"';}
+void __print(bool x) {cerr << (x ? "true" : "false");}
+ 
+template<typename T, typename V>
+void __print(const pair<T, V> &x);
+template<typename T>
+void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
+template<typename T, typename V>
+void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
+void _print() {cerr << "]\n";}
+template <typename T, typename... V>
+void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
+
+#ifdef DEBUG
+#define dbg(x...) cerr <<__func__<<":"<<__LINE__<<" [" << #x << "] = ["; _print(x); cerr << endl;
+#else
+#define dbg(x...)
+#endif
+
+mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
+
+struct custom_hash {
+    size_t operator()(uint64_t x) const {
+        x ^= rng();
+        return x ^ (x >> 16);
+    }
+};
+ 
+const int MOD = 1000000007;
+const char nl = '\n';
+const int MX = 100001; 
+
+/*
+ * DFS to find end times
+ * reverse graph
+ * find SCCs in reverse order
+*/
+
+void solve() {
+	int n, m; cin >> n >> m;
+	vector<vi> mp(n);
+	FOR (i, 0, m) {
+		int a, b; cin >> a >> b; a--; b--;
+		mp[a].pb(b);
+	}
+
+	int t = 0;
+	vector<bool> vis(n, false);
+	vi start(n), end(n);
+
+	auto dfs = [&](int node, auto&& self) -> void {
+		vis[node] = true;
+		start[node] = t++;
+		trav (neigh, mp[node]) {
+			if (!vis[neigh]) self(neigh, self);
+		}
+		end[node] = t++;
+	};
+
+	FOR (i, 0, n) if (!vis[i]) dfs(i, dfs);
+
+	vector<vi> mpR(n);
+	FOR (i, 0, n) {
+		trav (j, mp[i]) mpR[j].pb(i);
+	}
+
+	int kingdom = 0;
+	vi sccs(n);
+
+	auto dfs2 = [&](int node, auto&& self) -> void {
+		vis[node] = true;
+		sccs[node] = kingdom;
+		trav (neigh, mpR[node]) {
+			if (!vis[neigh]) self(neigh, self);
+		}
+	};
+
+	vpi order(n);
+	FOR (i, 0, n) order[i] = {end[i], i};
+	sort(order.begin(), order.end(), greater<pi>());
+
+	fill(vis.begin(), vis.end(), false);
+
+	FOR (i, 0, n) {
+		int node = order[i].sec;
+		if (vis[node]) continue;
+		kingdom++;
+		dfs2(node, dfs2);
+	}
+
+	cout << kingdom << nl;
+	trav (i, sccs) cout << i << ' ';
+	cout << nl;
+}
+ 
+int main() {
+    cin.tie(0)->sync_with_stdio(0); 
+    cin.exceptions(cin.failbit);
+ 
+    int T = 1;
+//    cin >> T;
+    while(T--) {
+        solve();
+    }
+ 
+	return 0;
+}
+