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  1. #include<cstdio>
  2. #include<cstdlib>
  3. #include<cstring>
  4. #include<algorithm>
  5. #include<iostream>
  6. #include<fstream>
  7. #include<map>
  8. #include<ctime>
  9. #include<set>
  10. #include<queue>
  11. #include<cmath>
  12. #include<vector>
  13. #include<bitset>
  14. #include<functional>
  15. #define x first
  16. #define y second
  17. #define mp make_pair
  18. #define pb push_back
  19. #define REP(i,l,r) for((i)=(l);(i)<=(r);++(i))
  20. #define REP2(i,l,r) for((i)=(l);(i)!=(r);++(i))
  21. using namespace std;
  22.  
  23. typedef long long LL;
  24. typedef double ld;
  25.  
  26. const int MAX=1000000+10;
  27.  
  28. int n;
  29. int ans;
  30. int fa[MAX];
  31.  
  32. int findfather(int u)
  33. {
  34. 	return u==fa[u]?u:fa[u]=findfather(fa[u]);
  35. }
  36.  
  37. int main()
  38. {
  39. 	int i,p;
  40. 	scanf("%d",&n);
  41. 	REP(i,1,n)
  42. 		fa[i]=i;
  43. 	REP(i,1,n)
  44. 	{
  45. 		scanf("%d",&p);
  46. 		fa[findfather(i)]=findfather(p);
  47. 	}
  48. 	REP(i,1,n)
  49. 		if(findfather(i)==i)
  50. 			++ans;
  51. 	cout<<ans<<endl;
  52. 	return 0;
  53. }
  54.  
Success #stdin #stdout 0s 7248KB
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https://ideone.com/MNeATK
language:
C++ (gcc 8.3)
created:
10 years ago
visibility:
secret

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