fork download 
  1. #include<iostream>
  2. #include<vector>
  3. using namespace std;
  4.  
  5. bool f(int n)
  6. {
  7. 	long long m = 1LL * n * n;
  8.  
  9. 	while (n)
  10. 	{
  11. 		if (n % 10 != m % 10) return false;
  12. 		n /= 10;
  13. 		m /= 10;
  14. 	}
  15.  
  16. 	return true;
  17. }
  18.  
  19. int main()
  20. {
  21. 	vector<int> L;
  22. 	for (int i = 0; i < 100000; i++)
  23. 	{
  24. 		long long n = i, m = 1LL * i * i;
  25. 		bool chk = true;
  26. 		for (int j = 0; j < 5; j++)
  27. 		{
  28. 			if (n % 10 != m % 10) chk = false;
  29. 			n /= 10;
  30. 			m /= 10;
  31. 		}
  32.  
  33. 		if (chk) L.push_back(i);
  34. 	}
  35.  
  36. 	long long N, ans = 0;
  37. 	cin >> N;
  38. 	for (int i = 0; i < 100000 && i < N; i++)
  39. 		if (f(i)) ans = i;
  40.  
  41. 	if (N >= 100000)
  42. 	{
  43. 		for (long long i = 100000; i <= N; i += 100000)
  44. 		{
  45. 			for (int j = 0; j < L.size(); j++)
  46. 			{
  47. 				long long val = i + L[j];
  48. 				if (val >= N) break;
  49.  
  50. 				if (f(val)) ans = val;
  51. 			}
  52. 		}
  53. 	}
  54. 	cout << ans;
  55. 	return 0;
  56. }
Success #stdin #stdout 0s 15240KB
comments (?)
stdin 
2147483647
stdout 
1787109376
https://ideone.com/nk1Ndf
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!