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1 files changed, 27 insertions, 0 deletions

diff --git a/racket/leetcode/lc-745-prefix-suffix.rkt b/racket/leetcode/lc-745-prefix-suffix.rkt
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+++ b/racket/leetcode/lc-745-prefix-suffix.rkt
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+#lang racket
+(define word-filter%
+  (class object%
+    (super-new)
+
+    ; words : (listof string?)
+    (init-field
+     words)                                                 ; Take in the provided dictionary.
+    (define word-ends-hash (make-hash))                     ; Make an empty hash table.
+    
+    (for/list ([w (in-list words)]                          ; For each word in the dictionary,
+               [index (in-naturals)])                       ; and its corresponding index,
+      (define len (string-length w))                        ; calculate its length,
+      (for*/list ([head (in-range 1 (min 11 (add1 len)))]   ; and for every combination of head length
+                  [tail (in-range 1 (min 11 (add1 len)))])  ; and tail length 
+        (hash-set! word-ends-hash                           ; from 1 to the max. affix length,
+                   (list (substring w 0 head)               ; set the key to the list containing
+                         (substring w (- len tail) len))    ; the prefix and suffix
+                   index)))                                 ; and map it to the word's index.
+    
+    ; f : string? string? -> exact-integer?
+    (define/public (f prefix suffix)                        ; Return the mapped value for the affixes
+      (hash-ref word-ends-hash (list prefix suffix) -1))))  ; or -1 if it doesn't exist.
+
+;; Your word-filter% object will be instantiated and called as such:
+;; (define obj (new word-filter% [words words]))
+;; (define param_1 (send obj f prefix suffix))
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