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1 files changed, 18 insertions, 0 deletions

diff --git a/racket/leetcode/lc-1844-replace-all-digits-with-characters.rkt b/racket/leetcode/lc-1844-replace-all-digits-with-characters.rkt
new file mode 100644
index 0000000..96aba6e
--- /dev/null
+++ b/racket/leetcode/lc-1844-replace-all-digits-with-characters.rkt
@@ -0,0 +1,18 @@
+#lang racket
+(define/contract (replace-digits s)
+  (-> string? string?)
+  (define/contract (shift-letter c x)
+    (-> char? char? char?)
+    (integer->char (+ (string->number (string x)) (char->integer c))))
+  (define letters (string->list (string-replace s #rx"[0-9]" "")))
+  (define digits (string->list (string-replace s #rx"[a-z]" "")))
+  (foldl (λ (c x acc)
+           (if (equal? x #\X)
+               (string-append acc (string c))
+               (string-append acc (string c) (string (shift-letter c x)))))
+         ""
+         letters
+         (if (= (length digits) (length letters))
+             digits
+             (append digits '(#\X)))
+         ))
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