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  1. #include <iostream>
  2. #include <vector>
  3. #include <math.h>
  4.  
  5. bool is_palindrome(int num)
  6. {
  7. 	std::vector<int> split_num;
  8. 	int max_exp = log10(num);
  9. 	int current_num = num;
  10. 	for (int e = max_exp; e >= 0; e--)
  11. 	{
  12. 		int power = (int)pow(10, e);
  13. 		split_num.push_back(current_num / power);
  14. 		current_num = current_num % power;
  15. 	}
  16. 	int length = split_num.size();
  17. 	for (int i = 0; i < length / 2; i++)
  18. 		if (split_num[i] != split_num[length - 1 - i])
  19. 			return false;
  20. 	return true;
  21. }
  22.  
  23. int main() {
  24. 	int max = 0;
  25. 	for (int i = 1000; i <= 9999; i++)
  26. 		for (int j = i; j <= 9999; j++) // wow! such optimization
  27. 		{
  28. 			int num = i * j;
  29. 			if (is_palindrome(num))
  30. 				if (num > max)
  31. 					max = num;
  32. 		}
  33. 	std::cout << max;
  34. 	return 0;
  35. }
Time limit exceeded #stdin #stdout 5s 3408KB
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https://ideone.com/dz0NTH
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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