p4.clj

(ns euler.p4)


(defn palindromic-number? [x]
  (let [arr (vec (.toString x)), size (count arr)]
    (loop [x 0]
      (if (not= (get arr x) (get arr (- size x 1)))
        false
      (if (> x (/ size 2))
        true
        (recur (inc x)))))))

       
 
(defn solve [start]
  (loop [col 0]
     (def coltry
      (for [
            x (reverse (if (= col 0) 
                    (range 1) 
                    (range col (- col 
                                  (int (Math/ceil (/ col 2))) 
                                  (if (even? col) 1 0))
                           -1)
                    ))     
            :let [y (- col x), n1 (- start x), n2 (- start y), p (* n1 n2), found false]
            :when (palindromic-number? p)
           ]
        [p n1 n2])
       )
    (if (not-empty coltry)
      (println (first coltry))
      (when (< col start)
        (recur (inc col))))))
      
  
(time (solve 999))