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36 lines
850 B
C++
36 lines
850 B
C++
#define _CRT_SECURE_NO_WARNINGS
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#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
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#include <bits/stdc++.h>
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using namespace std;
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const int N = 1050;
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bool vis[N];
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int nxt[N], n;
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void dfs(int x)
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{
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for (int i = 1; i <= n; i++)
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if (nxt[i] != i && !vis[nxt[i]])
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{
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vis[nxt[i]] = true;
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dfs(nxt[i]);
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}
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}
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int main()
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{
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scanf("%d", &n);
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for (int i = 1; i <= n; i++)
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{
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int a, b;
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scanf("%d%d", &a, &b);
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nxt[a] = b;
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}
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int ans = n;
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for (int i = 1; i <= n; i++)
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for (int j = 1; j <= n; j++)
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if (nxt[i] == j && !vis[j] && j != i)
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vis[j] = true, ans--;
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//for (int i = 1; i <= n; i++) dfs(i);
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//printf("%d", accumulate(vis + 1, vis + n + 1, 0, [](auto a, auto b) { return a + !b; }));
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printf("%d", ans);
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return 0;
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}
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