tasks a-s

Task/Pythagorean-triples/OCaml/pythagorean-triples.ocaml

@@ -0,0 +1,33 @@
+let isqrt n =
+   let rec iter t =
+      let d = n - t*t in
+      if (0 <= d) && (d < t+t+1) (* t*t <= n < (t+1)*(t+1) *)
+      then t else iter ((t+(n/t))/2)
+   in iter 1
+
+let rec gcd a b =
+   let t = a mod b in
+   if t = 0 then b else gcd b t
+
+let coprime a b = gcd a b = 1
+
+let num_to ms =
+   let ctr = ref 0 in
+   let prim_ctr = ref 0 in
+   let max_m = isqrt (ms/2) in
+   for m = 2 to max_m do
+      for j = 0 to (m/2) - 1 do
+         let n = m-(2*j+1) in
+         if coprime m n then
+            let s = 2*m*(m+n) in
+            if s <= ms then
+               (ctr := !ctr + (ms/s); incr prim_ctr)
+      done
+   done;
+  (!ctr, !prim_ctr)
+
+let show i =
+  let s, p = num_to i in
+  Printf.printf "For perimeters up to %d there are %d total and %d primitive\n%!" i s p;;
+
+List.iter show [ 100; 1000; 10000; 100000; 1000000; 10000000; 100000000 ]