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@@ -0,0 +1,16 @@
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+#lang racket
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+
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+;; https://leetcode.com/problems/two-sum/description/
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+
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+(define/contract (two-sum nums target)
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+ (-> (listof exact-integer?) exact-integer? (listof exact-integer?))
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+ (define h (make-hash))
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+ (define (loop nums index)
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+ (define n (car nums))
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+ (define diff (- target n))
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+ (if (hash-has-key? h diff)
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+ (list index (hash-ref h diff))
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+ (let ()
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+ (hash-set! h n index)
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+ (loop (cdr nums) (+ 1 index)))))
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+ (loop nums 0))
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