new files

Task/Knuth-shuffle/Fortran/knuth-shuffle.f

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+program Knuth_Shuffle
+  implicit none
+
+  integer, parameter :: reps = 1000000
+  integer :: i, n
+  integer, dimension(10) :: a, bins = 0, initial = (/ (n, n=1,10) /)
+
+  do i = 1, reps
+    a = initial
+ 	call Shuffle(a)
+    where (a == initial) bins = bins + 1  ! skew tester
+  end do
+  write(*, "(10(i8))") bins
+! prints  100382  100007   99783  100231  100507   99921   99941  100270  100290  100442
+
+contains
+
+subroutine Shuffle(a)
+  integer, intent(inout) :: a(:)
+  integer :: i, randpos, temp
+  real :: r
+
+  do i = size(a), 2, -1
+    call random_number(r)
+    randpos = int(r * i) + 1
+    temp = a(randpos)
+    a(randpos) = a(i)
+    a(i) = temp
+  end do
+
+end subroutine Shuffle
+
+end program Knuth_Shuffle