tasks a-s

Task/Pythagorean-triples/Fortran/pythagorean-triples.f

@@ -0,0 +1,46 @@
+module triples
+  implicit none
+
+  integer :: max_peri, prim, total
+  integer :: u(9,3) = reshape((/ 1, -2, 2,  2, -1, 2,  2, -2, 3, &
+                                 1,  2, 2,  2,  1, 2,  2,  2, 3, &
+                                -1,  2, 2, -2,  1, 2, -2,  2, 3 /), &
+                                (/ 9, 3 /))
+
+contains
+
+recursive subroutine new_tri(in)
+  integer, intent(in) :: in(:)
+  integer :: i
+  integer :: t(3), p
+
+  p = sum(in)
+  if (p > max_peri) return
+
+  prim = prim + 1
+  total = total + max_peri / p
+  do i = 1, 3
+    t(1) = sum(u(1:3, i) * in)
+    t(2) = sum(u(4:6, i) * in)
+    t(3) = sum(u(7:9, i) * in)
+    call new_tri(t);
+  end do
+end subroutine new_tri
+end module triples
+
+program Pythagorean
+  use triples
+  implicit none
+
+  integer :: seed(3) = (/ 3, 4, 5 /)
+
+  max_peri = 10
+  do
+    total = 0
+    prim = 0
+    call new_tri(seed)
+    write(*, "(a, i10, 2(i10, a))") "Up to", max_peri, total, " triples",  prim, " primitives"
+    if(max_peri == 100000000) exit
+    max_peri = max_peri * 10
+  end do
+end program Pythagorean