fork download 
  1. #include <iostream>
  2.  
  3. int H(int n, int x)   // recursive version
  4. {
  5. 	if (n <= 0)      
  6. 		return -1;
  7. 	else if (n == 1) 
  8. 		return 1;
  9. 	else if (n == 2) 
  10. 		return 2 * x;
  11. 	else 
  12. 		return 2 * x * H(n-1, x) - 2 * n * H(n - 2, x); // shift n+1, n n-1 to n, n-1 n-2 
  13. }
  14.  
  15. int Hi(int n, int x) //iterative version
  16. {
  17. 	if (n <= 0)      
  18. 		return -1;
  19. 	else if (n == 1) 
  20. 		return 1;
  21.  
  22. 	int am2 = 1;      // start for for n-2
  23.     int am1 = 2*x;    // start for n-1
  24. 	if (n == 2) 
  25. 		return am1;
  26.  
  27.     int am; 
  28.     for (int i=3; i<=n; i++) {
  29.     	am = 2*x*am1 -  2*i*am2;
  30.     	//prepare next interation
  31.     	am2=am1; 
  32.     	am1=am;
  33.     }
  34. 	return am; 
  35. }
  36.  
  37.  
  38. int main()
  39. {
  40. int n, x;
  41. //std::cout << "Enter the number n: ";
  42. //std::cin >> n;
  43. //std::cout << "Enter the number x: ";
  44. //std::cin >> x;
  45.  
  46. for (x=5, n=1; n<6; n++) {  
  47. 	std::cout << n<<" "<<x<<" Rec = " << H(n, x) << " Iter = " << Hi(n,x) << std::endl;
  48.  	}
  49. }
Success #stdin #stdout 0s 15240KB
comments (?)
stdin 
Standard input is empty
stdout 
1 5 Rec = 1 Iter = 1
2 5 Rec = 10 Iter = 10
3 5 Rec = 94 Iter = 94
4 5 Rec = 860 Iter = 860
5 5 Rec = 7660 Iter = 7660
https://ideone.com/HKLy78
language:
C++14 (gcc 8.3)
created:
6 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!