1183. 电力

https://www.acwing.com/problem/content/submission/code_detail/9945178/

AcWing/1183/1183.cpp

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+#include <array>
+#include <iostream>
+#include <stack>
+#include <vector>
+
+using std::cin;
+using std::cout;
+using std::endl;
+
+const int N = 10005;
+
+int ans;
+std::array<std::vector<int>, N> g;
+
+// Tarjan
+int root;
+std::array<int, N> dfn;
+int cnt, low[N];
+int dcc_cnt, id[N];
+std::stack<int> st;
+
+void tarjan(int);
+
+int main() {
+    int n, m;
+    while (cin >> n >> m, n || m) {
+        ans = dcc_cnt = cnt = 0;
+        dfn.fill(0);
+        g.fill({});
+        for (int i = 1; i <= m; i++) {
+            int a, b;
+            cin >> a >> b;
+            g[a + 1].push_back(b + 1);
+            g[b + 1].push_back(a + 1);
+        }
+        for (int i = 1; i <= n; i++) {
+            if (!dfn[i]) {
+                root = i;
+                dcc_cnt++;
+                tarjan(i);
+            }
+        }
+        cout << ans + dcc_cnt - 1 << endl;
+    }
+    return 0;
+}
+
+void tarjan(int u) {
+    dfn[u] = low[u] = ++cnt;
+    int size = 0;
+    for (int v : g[u]) {
+        if (!dfn[v]) {
+            tarjan(v);
+            low[u] = std::min(low[u], low[v]);
+            if (low[v] >= dfn[u]) size++;
+        } else {
+            low[u] = std::min(low[u], dfn[v]);
+        }
+    }
+    if (u != root) size++;
+    ans = std::max(ans, size);
+}