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  1. // Calculate Nth Fibbionacci number in O(log N)
  2. import java.util.Scanner;
  3. object Main{
  4. 	// Matrix multiplication
  5. 	def matmul(mat1 : Array[ Array [Int] ], mat2 : Array[ Array [Int] ]): Array[ Array [Int] ] = {
  6. 		val n = mat1.size;
  7. 		var res = new Array[ Array [Int]](n, n);
  8. 		for(i <- 0 until n){
  9. 			for(j <- 0 until n){
  10. 				res(i)(j) = 0;
  11. 				for(k <- 0 until n){
  12. 					res(i)(j) += mat1(i)(k) * mat2(k)(j);
  13. 				}
  14. 			}
  15. 		}
  16. 		return res;
  17. 	}
  18. 	// Matrix powering
  19. 	def matpow(mat : Array[ Array [Int] ], p : Int): Array[ Array [Int] ] = {
  20. 		val n = mat.size;
  21. 		var pow = p;
  22. 		var par, res = new Array[ Array [Int]](n, n);
  23. 		for(i <- 0 until n){
  24. 			for(j <- 0 until n){
  25. 				par(i)(j) = mat(i)(j);
  26. 				if(i == j) res(i)(j) = 1;
  27. 				else res(i)(j) = 0;
  28. 			}
  29. 		}
  30. 		while(pow > 0){
  31. 			if(pow % 2 == 1){
  32. 				res = matmul(res, par);
  33. 			}
  34. 			par = matmul(par, par);
  35. 			pow /= 2;
  36. 		}
  37. 		return res;
  38. 	}
  39. 	// Calculate sum of a
  40. 	def fibb(n : Int): Int = {
  41. 		var mat = new Array[ Array [Int]](2, 2);
  42. 		mat(0)(0) = 1; mat(0)(1) = 1; mat(1)(0) = 1; mat(1)(1) = 0;
  43. 		mat = matpow(mat, n);
  44. 		return mat(1)(0);
  45. 	}
  46. 	// Main function
  47. 	def main(args : Array[ String ]) = {
  48. 		val in = new Scanner(System.in);
  49. 		val num = in.nextInt();
  50. 		println(fibb(num));
  51. 	}
  52. }
  53.  
Runtime error #stdin #stdout 0.04s 211456KB
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https://ideone.com/f8Ezq
language:
Scala (scala 2.12.8)
created:
14 years ago
visibility:
public

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