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1987 - 小丑竟在我身边
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bjtu/1987/1987.cpp
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48
bjtu/1987/1987.cpp
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#include <iostream>
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#include <vector>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 1e4 + 5;
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int n, m, cnt, cnt2;
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std::vector<int> g[N];
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bool vis[N], flag = true;
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void dfs(int u) {
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cnt++;
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vis[u] = true;
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for (int v : g[u]) {
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if (!vis[v]) dfs(v);
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}
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> m;
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for (int i = 1, u, v; i <= m; i++) {
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cin >> u >> v;
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g[u].emplace_back(v);
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g[v].emplace_back(u);
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}
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for (int i = 1; i <= n; i++) {
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if (!vis[i]) {
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int pre = cnt;
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dfs(i);
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if (cnt - pre > 1) cnt2++;
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}
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}
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cout << (cnt2 <= 1 ? "YES" : "NO") << endl;
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return 0;
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}
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