46 lines
1.3 KiB
Factor
46 lines
1.3 KiB
Factor
! Copyright (c) 2012 Anonymous
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! See http://factorcode.org/license.txt for BSD license.
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USING: arrays locals math math.ranges sequences sets sorting ;
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IN: rosetta-code.count-the-coins
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! http://rosettacode.org/wiki/Count_the_coins
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! There are four types of common coins in US currency: quarters
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! (25 cents), dimes (10), nickels (5) and pennies (1). There are 6
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! ways to make change for 15 cents:
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! A dime and a nickel;
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! A dime and 5 pennies;
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! 3 nickels;
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! 2 nickels and 5 pennies;
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! A nickel and 10 pennies;
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! 15 pennies.
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! How many ways are there to make change for a dollar using
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! these common coins? (1 dollar = 100 cents).
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! Optional:
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! Less common are dollar coins (100 cents); very rare are half
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! dollars (50 cents). With the addition of these two coins, how
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! many ways are there to make change for $1000? (note: the answer
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! is larger than 232).
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<PRIVATE
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:: (make-change) ( cents coins -- ways )
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cents 1 + 0 <array> :> ways
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1 ways set-first
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coins [| coin |
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coin cents [a,b] [| j |
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j coin - ways nth j ways [ + ] change-nth
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] each
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] each ways last ;
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PRIVATE>
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! How many ways can we make the given amount of cents
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! with the given set of coins?
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: make-change ( cents coins -- ways )
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members [ ] inv-sort-with (make-change) ;
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