tasks a-s

Task/Non-continuous-subsequences/R/non-continuous-subsequences.r

@@ -0,0 +1,17 @@
+ncsub <- function(x)
+{
+   n <- length(x)
+   a <- seq_len(n)
+   seqlist <- list()
+   for(i in 2:(n-1))
+   {
+      seqs <- combn(a, i)                                                          # Get all subseqs
+      ok <- apply(seqs, 2, function(x) any(diff(x)!=1))                            # Find noncts ones
+      newseqs <- unlist(apply(seqs[,ok], 2, function(x) list(x)), recursive=FALSE) # Convert matrix to list of its columns
+      seqlist <- c(seqlist, newseqs)                                               # Append to existing list
+   }
+   lapply(seqlist, function(index) x[index])
+}
+# Example usage
+ncsub(1:4)
+ncsub(letters[1:5])