Add q73.. this was rough

src/ex/q073.clj

@@ -0,0 +1,15 @@
+;; https://4clojure.oxal.org/#/problem/073
+
+(ns ex.q073)
+
+(defn ans
+  "Problem 73, Analyze a Tic-Tac-Toe Board"
+  [board]
+  (letfn [(win? [coll] (if (and (apply = coll) (not= (first coll) :e)) (first coll) nil))
+          (transpose [coll] (apply map vector coll))
+          (diag [coll i] (map (fn [[idx row]] (row idx)) (zipmap i coll)))]
+    (first (drop-while nil?
+                       (lazy-cat
+                        (map win? board)
+                        (map win? (transpose board))
+                        (map win? [(diag board [0 1 2]) (diag board [2 1 0])]))))))

test/ex/q073_test.clj

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+;; https://4clojure.oxal.org/#/problem/073
+
+(ns ex.q073-test
+  (:require [clojure.test :as t]
+            [ex.q073 :as sut]))
+
+(t/deftest test-q73
+  (t/testing "Problem 73, Analyze a Tic-Tac-Toe Board"
+    (t/is (= nil (sut/ans [[:e :e :e]
+                           [:e :e :e]
+                           [:e :e :e]])))
+    (t/is (= :x (sut/ans [[:x :e :o]
+                          [:x :e :e]
+                          [:x :e :o]])))
+    (t/is (= :o (sut/ans [[:e :x :e]
+                          [:o :o :o]
+                          [:x :e :x]])))
+    (t/is (= nil (sut/ans [[:x :e :o]
+                           [:x :x :e]
+                           [:o :x :o]])))
+    (t/is (= :x (sut/ans [[:x :e :e]
+                          [:o :x :e]
+                          [:o :e :x]])))
+    (t/is (= :o (sut/ans [[:x :e :o]
+                          [:x :o :e]
+                          [:o :e :x]])))
+    (t/is (= nil (sut/ans [[:x :o :x]
+                           [:x :o :x]
+                           [:o :x :o]])))))