From fafbeaf9e3c09ba7a5bea7e47d5736001f8a5aa1 Mon Sep 17 00:00:00 2001
From: HJ <thechairman@thechairman.info>
Date: Tue, 17 Jan 2023 12:46:04 -0500
Subject: adding old leetcode solutions

---
 leetcode/lc-953-alien-dictionary.rkt | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
 create mode 100644 leetcode/lc-953-alien-dictionary.rkt

(limited to 'leetcode/lc-953-alien-dictionary.rkt')

diff --git a/leetcode/lc-953-alien-dictionary.rkt b/leetcode/lc-953-alien-dictionary.rkt
new file mode 100644
index 0000000..f72a895
--- /dev/null
+++ b/leetcode/lc-953-alien-dictionary.rkt
@@ -0,0 +1,26 @@
+#lang racket
+
+(define/contract (is-alien-sorted words order)
+  (-> (listof string?) string? boolean?)
+  (define alpha-order
+    (make-hash (map (λ (a b) (cons a b))
+                    (map string (string->list order))
+                    (build-list (string-length order) identity))))
+  (hash-set! alpha-order #\* -1)
+  (define (alien<? s1 s2)
+    (cond [(equal? s1 "") #true]
+          [(equal? s2 "") #false]
+          [(equal? (hash-ref alpha-order (substring s1 0 1))
+                   (hash-ref alpha-order (substring s2 0 1)))
+           (alien<? (substring s1 1 (string-length s1))
+                    (substring s2 1 (string-length s2)))]
+          [(< (hash-ref alpha-order (substring s1 0 1))
+              (hash-ref alpha-order (substring s2 0 1))) #true]
+          [else false]))
+  (equal? words
+          (sort words alien<?)))
+
+(is-alien-sorted '["hello" "leetcode"] "hlabcdefgijkmnopqrstuvwxyz")
+(is-alien-sorted '["word" "world" "row"] "worldabcefghijkmnpqstuvxyz")
+(is-alien-sorted '["apple" "app"] "abcdefghijklmnopqrstuvwxyz")
+(is-alien-sorted '["iekm" "tpnhnbe"] "loxbzapnmstkhijfcuqdewyvrg")
\ No newline at end of file
-- 
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