mirror of
https://git.sb/baoshuo/OI-codes.git
synced 2024-12-02 23:56:29 +00:00
77 lines
1.4 KiB
C++
77 lines
1.4 KiB
C++
#include <iostream>
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#include <stack>
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using std::cin;
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using std::cout;
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using std::endl;
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const int N = 5005,
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M = 10005;
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int f, r, ans;
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// Graph
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int idx, head[N], edge[M], next[M];
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void add(int u, int v) {
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next[idx] = head[u];
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edge[idx] = v;
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head[u] = idx++;
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}
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// Tarjan
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int cnt, dfn[N], low[N];
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int dcc_cnt, id[N];
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std::stack<int> st;
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int deg[N];
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bool bridge[N];
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void tarjan(int u, int in_edge) {
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dfn[u] = low[u] = ++cnt;
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st.push(u);
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for (int i = head[u]; ~i; i = next[i]) {
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int v = edge[i];
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if (!dfn[v]) {
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tarjan(v, i);
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low[u] = std::min(low[u], low[v]);
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if (dfn[u] < low[v]) {
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bridge[i] = bridge[i ^ 1] = true;
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}
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} else if (i != (in_edge ^ 1)) {
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low[u] = std::min(low[u], dfn[v]);
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}
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}
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if (low[u] == dfn[u]) {
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dcc_cnt++;
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int v;
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do {
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v = st.top();
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st.pop();
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id[v] = dcc_cnt;
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} while (v != u);
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}
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}
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int main() {
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std::fill(head, head + N, -1);
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cin >> f >> r;
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for (int i = 1; i <= r; i++) {
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int u, v;
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cin >> u >> v;
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add(u, v);
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add(v, u);
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}
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tarjan(1, -1);
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for (int i = 0; i < idx; i++) {
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if (bridge[i]) {
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deg[id[edge[i]]]++;
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}
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}
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for (int i = 1; i <= dcc_cnt; i++) {
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if (deg[i] == 1) ans++;
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}
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cout << (ans + 1 >> 1) << endl;
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return 0;
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}
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