Advent of Clojure solutions

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solution.clj

(ns advent-of-clojure.core)

(defn next-val [prev]
  (mod (* 252533 prev) 33554393))

(defn sum-all [x]
  (/ (* x (inc x)) 2))

(defn full-diags [x y]
  (- (+ x y) 2))

(defn seq-idx [x y]
  (let [diags (full-diags x y)]
    (dec (+ y (sum-all diags)))))

(defn seq-gen [init]
  (lazy-seq (cons init (seq-gen (next-val init)))))

(defn solve
  "Solving https://adventofcode.com/2015/day/25"
  [x y]
  (nth (seq-gen 20151125)
       (seq-idx x y)))


(comment

  (let [x 42] (inc x))

  ((fn [x] (inc x))) 42)