'commit'

TangDou/AcWing/SCC/1175_Prepare.cpp

@@ -0,0 +1,64 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+const int N = 100010, M = 2000010; // 因为要建新图，两倍的边
+int n, m, mod;                     // 点数、边数、取模的数
+
+int f[N], g[N];
+
+int h[N], hs[N], e[M], ne[M], idx; // h: 原图；hs: 新图
+void add(int a, int b) {
+    e[idx] = b, ne[idx] = h[a], h[a] = idx++;
+}
+
+// tarjan求强连通分量
+int dfn[N], low[N], ts, in_stk[N], stk[N], top;
+int id[N], scc_cnt, sz[N];
+void tarjan(int u) {
+    dfn[u] = low[u] = ++ts;
+    stk[++top] = u;
+    in_stk[u] = 1;
+    for (int i = h[u]; ~i; i = ne[i]) {
+        int v = e[i];
+        if (!dfn[v]) {
+            tarjan(v);
+            low[u] = min(low[u], low[v]);
+        } else if (in_stk[v])
+            low[u] = min(low[u], low[v]);
+    }
+    if (dfn[u] == low[u]) {
+        ++scc_cnt;
+        int x;
+        do {
+            x = stk[top--];
+            in_stk[x] = 0;
+            id[x] = scc_cnt;
+            sz[scc_cnt]++;
+        } while (x != u);
+    }
+}
+int main() {
+#ifndef ONLINE_JUDGE
+    freopen("1175_Preapre.in", "r", stdin);
+#endif
+    memset(h, -1, sizeof h); // 原图
+
+    scanf("%d %d", &n, &m);
+
+    while (m--) {
+        int a, b;
+        scanf("%d %d", &a, &b);
+        add(a, b);
+    }
+    // (1) tarjan算法求强连通分量
+    for (int i = 1; i <= n; i++)
+        if (!dfn[i]) tarjan(i);
+
+    for (int i = 1; i <= n; i++)
+        cout << "id[" << i << "]=" << id[i] << " ";
+    cout << endl;
+
+    cout << "scc_cnt=" << scc_cnt << endl;
+
+    return 0;
+}