Day 2 Notebook

input<-read_lines("Day2Sample.txt")


#### Original
#reports<-list()
#for (i in 1:length(input)){
#  reports<-c(reports,list(as.numeric(unlist(str_split(input[i]," ")))))}
### Updated after online help/suggestion

reports<-lapply(str_split(input, " "),as.numeric)

Part 1

Uses diff() to see the difference between the elements in the vector. Then checks to see if they’re all either between 1 & 3 or -1 & -3

issafe<-function(rprt){
  d<-diff(rprt)
  if((all(d>=1)&&all(d<=3))||(all(d<=-1)&&all(d>=-3))){
    d<-TRUE}else{d<-FALSE}
  d}

counts the number of vectors that are safe

part1<-sum(sapply(reports,issafe))
part1

[1] 2

Part 2

check with the problem dampener

probdamp<-function(rpt){
  ### if it is safe, return TRUE
  if(issafe(rpt)){return(TRUE)}
  ### otherwise, set to false
  pd<-FALSE
  i<-1
  ### cycle through removing level one at a time
  ### stop as soon as either a level is removed that makes the report safe
  ### or there aren't any left to try to remove
  while(!pd&&i<=length(rpt)){
    pd<-issafe(rpt[-i])
  i<-i+1}
  return(pd)}

part2<-sum(sapply(reports,probdamp))
part2

[1] 4