Day 4 Notebook

input<-read_lines("Day4Sample.txt")

### put the wordsearch in a matrix
wordsearch<-matrix(nrow=length(input),ncol=nchar(input[1]))
for(i in 1:length(input)){wordsearch[i,]<-unlist(str_split(input[i],""))}

Part 1

I feel like this is a horrible idea. But, just looking in all 8 directions around an X works.

lookingforxmas<-function(wsm){
  xmascounter<-0
  for(x in 1:ncol(wsm)){
    for(y in 1:nrow(wsm)){
      ## Check to see if it's an "X" otherwise move on
      if(wsm[y,x]!="X"){
        next}else{
          ### check up
          if(y>=4){
            if(wsm[y-1,x]=="M"&&wsm[y-2,x]=="A"&&wsm[y-3,x]=="S"){xmascounter<-xmascounter+1}}
          ### check up right
          if(y>=4&&x<=(ncol(wsm)-3)){
            if(wsm[y-1,x+1]=="M"&&wsm[y-2,x+2]=="A"&&wsm[y-3,x+3]=="S"){xmascounter<-xmascounter+1}}
          ### check right
          if(x<=(ncol(wsm)-3)){
            if(wsm[y,x+1]=="M"&&wsm[y,x+2]=="A"&&wsm[y,x+3]=="S"){xmascounter<-xmascounter+1}}
          ### check down right
          if(x<=(ncol(wsm)-3)&&y<=(nrow(wsm)-3)){
            if(wsm[y+1,x+1]=="M"&&wsm[y+2,x+2]=="A"&&wsm[y+3,x+3]=="S"){xmascounter<-xmascounter+1}}
          ### check down
          if(y<=(nrow(wsm)-3)){
            if(wsm[y+1,x]=="M"&&wsm[y+2,x]=="A"&&wsm[y+3,x]=="S"){xmascounter<-xmascounter+1}}
          ### check down left
          if(y<=(nrow(wsm)-3)&&x>=4){
            if(wsm[y+1,x-1]=="M"&&wsm[y+2,x-2]=="A"&&wsm[y+3,x-3]=="S"){xmascounter<-xmascounter+1}}
          ### check left
          if(x>=4){
            if(wsm[y,x-1]=="M"&&wsm[y,x-2]=="A"&&wsm[y,x-3]=="S"){xmascounter<-xmascounter+1}}
          ### check up left
          if(x>=4&&y>=4){
            if(wsm[y-1,x-1]=="M"&&wsm[y-2,x-2]=="A"&&wsm[y-3,x-3]=="S"){xmascounter<-xmascounter+1}}
        }
    }
  }
  
xmascounter}

part1<-lookingforxmas(wordsearch)
part1

[1] 18

Part 1 - real data

Part 2

Same thing, but look for M’s on the top, right, bottom, left of an A.

lookingforcrossedmas<-function(wsm){
  mascounter<-0
  ### only check for A's that aren't on the edges
  for(x in 2:(ncol(wsm)-1)){
    for(y in 2:(nrow(wsm)-1)){
      ## Check to see if it's an "X" otherwise move on
      if(wsm[y,x]!="A"){
        next}else{
          ### Clockwise MMSS
          if(wsm[y-1,x-1]=="M"&&wsm[y-1,x+1]=="M"&&wsm[y+1,x+1]=="S"&&wsm[y+1,x-1]=="S"){mascounter<-mascounter+1}
          ### Clockwise SMMS
          if(wsm[y-1,x-1]=="S"&&wsm[y-1,x+1]=="M"&&wsm[y+1,x+1]=="M"&&wsm[y+1,x-1]=="S"){mascounter<-mascounter+1}
          ### Clockwise SSMM
          if(wsm[y-1,x-1]=="S"&&wsm[y-1,x+1]=="S"&&wsm[y+1,x+1]=="M"&&wsm[y+1,x-1]=="M"){mascounter<-mascounter+1}
          ### Clockwise MSSM
          if(wsm[y-1,x-1]=="M"&&wsm[y-1,x+1]=="S"&&wsm[y+1,x+1]=="S"&&wsm[y+1,x-1]=="M"){mascounter<-mascounter+1}
          
        }}}
  mascounter}

part2<-lookingforcrossedmas(wordsearch)
part2

[1] 9

Part 2 - real data