core.clj

(ns sudoku-validator.core)

(defn is-valid-solution [grid]
  (let [rows (partition-all 9 (map (comp read-string str) grid))
        cols (apply map (comp seq vector) rows)
        squares (map
                  flatten
                  (partition-all
                    3
                    (for [base (range 3)
                          row rows
                          range (take-nth
                                  3
                                  (partition-all 3 (drop (* 3 base) row)))]
                      range)))]

    (every? (fn [group]
              (= (set (range 1 10))
                 (set (map (comp read-string str) group))))
            (concat rows cols squares))))

core_test.clj

(ns sudoku-validator.core-test
  (:require [clojure.test :refer :all]
            [sudoku-validator.core :refer :all]))

(deftest is-valid-solution-test
  (testing "true if sudoku is valid"
    (is (= true (is-valid-solution "835416927296857431417293658569134782123678549748529163652781394981345276374962815")))))