Solution for #39.

src/projecteuler/p039.clj

@@ -0,0 +1,28 @@
+(ns projecteuler.core)
+
+;; https://projecteuler.net/problem=39
+
+(defn- euclid-solutions [m n max]
+  (let [a (- (* m m) (* n n))
+        b (* 2 m n)
+        c (+ (* m m) (* n n))
+        p (+ a b c)
+        q (quot max p)]
+    (map #(vec (sort (list (* a %) (* b %) (* c %) (* p %))))
+         (range 1 (inc q)))))
+(defn- get-euclid-solutions [max-p]
+  (let [max-n (int (Math/sqrt (/ max-p 2)))
+        max-m (inc max-n)]
+    (loop [m 1, c #{}]
+      (cond
+       (> m max-m) c
+       :else (recur (inc m)
+                    (set (reduce concat c
+                                 (map #(euclid-solutions % m max-p)
+                                      (range (inc m) max-n 2)))))))))
+
+(defn int-right-triangles-max [& [max]]
+  (let [max (or max 999)]
+    (first (first (sort #(compare (count (second %2))
+                                  (count (second %1)))
+                        (group-by last (get-euclid-solutions max)))))))