数组的复杂问题 ACM(Array Complicated Manipulation)

Question

Problem Description
Given an infinite array of integers 2,3,.... Now do some operations on it.

The operation is to choose a minimum number from the array which is never been chosen, then change the status of its multiples excluding itself, i.e remove the multiples of the chosen number if they are in the array , otherwise add it to the array.keep the order after change.

For instance, the first step, choose number 2, change the status of 4, 6, 8, 10... They are all removed from the array. The second step, choose 3, change the status of 6, 9, 12, 15...

Pay attention: 9 and 15 are removed from the array while 6 and 12 are added to the array.

Input
Every line contains an integer n. The zero value for n indicates the end of input.

Output
Print "yes" or "no" according whether n is in the array.

Sample Input
2
30
90
0

Sample Output
yes
yes
no

Answer 1

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# read data
data <- readLines()

# initialize result list
res <- c("yes", "yes")

# iterate through each line
for (i in 2:length(data)) {
  # get current line's integer value
  val <- as.integer(substr(data[i], 1, -1))
  
  # check if val exists in res
  if (!any(res == val)) {
    # find all multiples of val that are not in res
    mults <- unique(which(val %in% data) %in% res & !val %in% res)
    
    # remove those multiples from res
    res[!mults] <- ""
    
    # add new multiples to res
    res <- paste(c(res, paste(mults)), collapse = ", ")
  }
}

# print result
print(res)