Perfect shuffle: Difference between revisions
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ReeceGoding (talk | contribs) (→{{header|R}}: Gave new solution. Cleaned up formatting of older one.) |
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=={{header|R}}== |
=={{header|R}}== |
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===Matrix solution=== |
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<lang R> |
<lang R>wave.shuffle <- function(n) { |
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wave.shuffle <- function(n) { |
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deck <- 1:n ## create the original deck |
deck <- 1:n ## create the original deck |
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new.deck <- c(matrix(data = deck, ncol = 2, byrow = TRUE)) ## shuffle the deck once |
new.deck <- c(matrix(data = deck, ncol = 2, byrow = TRUE)) ## shuffle the deck once |
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test <- sapply(test.values, wave.shuffle) ## apply the wave.shuffle function on each element |
test <- sapply(test.values, wave.shuffle) ## apply the wave.shuffle function on each element |
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names(test) <- test.values ## name the result |
names(test) <- test.values ## name the result |
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test ## print the result out |
test ## print the result out</lang> |
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{{out}} |
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> test |
<pre>> test |
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8 24 52 100 1020 1024 10000 |
8 24 52 100 1020 1024 10000 |
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3 11 8 30 1018 10 300 |
3 11 8 30 1018 10 300</pre> |
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===Sequence solution=== |
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</lang> |
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The previous solution exploits R's matrix construction; This solution exploits its array indexing. |
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<lang R>#A strict reading of the task description says that we need a function that does exactly one shuffle. |
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pShuffle<-function(deck) |
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{ |
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n<-length(deck)#Assumed even (as in task description). |
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new<-array(n)#Maybe not as general as it could be, but the task said to use whatever was convenient. |
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new[seq(from=1,to=n,by=2)]<-deck[seq(from=1,to=n/2,by=1)] |
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new[seq(from=2,to=n,by=2)]<-deck[seq(from=1+n/2,to=n,by=1)] |
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new |
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} |
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task2<-function(deck) |
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{ |
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new<-deck |
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count<-0 |
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repeat |
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{ |
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new<-pShuffle(new) |
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count<-count+1 |
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if(all(new==deck)){break} |
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} |
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cat("It takes",count,"shuffles of a deck of size",length(deck),"to return to the original deck.","\n") |
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invisible(count)#For the unit tests. The task wanted this printed so we only return it invisibly. |
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} |
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#Tests - All done in one line. |
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mapply(function(x,y) task2(1:x)==y,c(8,24,52,100,1020,1024,10000),c(3,11,8,30,1018,10,300))</lang> |
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{{out}} |
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<pre>> mapply(function(x,y) task2(1:x)==y,c(8,24,52,100,1020,1024,10000),c(3,11,8,30,1018,10,300)) |
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It takes 3 shuffles of a deck of size 8 to return to the original deck. |
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It takes 11 shuffles of a deck of size 24 to return to the original deck. |
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It takes 8 shuffles of a deck of size 52 to return to the original deck. |
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It takes 30 shuffles of a deck of size 100 to return to the original deck. |
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It takes 1018 shuffles of a deck of size 1020 to return to the original deck. |
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It takes 10 shuffles of a deck of size 1024 to return to the original deck. |
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It takes 300 shuffles of a deck of size 10000 to return to the original deck. |
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[1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE</pre> |
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=={{header|Racket}}== |
=={{header|Racket}}== |
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