AdventOfCodeSolutions/2024/day4/part1.js

#!/usr/bin/env node


var input = require('fs').readFileSync(process.argv[2]||'input.txt','utf8').split('\n').filter(i=>i);
//Make many versions of the data in different orientations
//All modes are an array of buffers.  We will turn them into arrays of strings soon.
var mode0 = input.map(i=>Buffer.from(i));
//Width and height happen to be equal.. 140
var width = mode0[0].length;
var height = mode0.length;
//Transpose mode1
var mode1 = [];
for(var i=0;i<width;++i) { //Allocate
 mode1.push(Buffer.alloc(height));
}
for(var i=0;i<height;++i) {
 for(var j=0;j<width;++j) {
  mode1[j][i]=mode0[i][j];
 }
}
//Diaganal mode2
var mode2 = [];
for(var i=1;i<=width;++i) { //Allocate half
 mode2.push(Buffer.alloc(i));
}
for(var i=width-1;i>0;--i) { //Allocate second half
 mode2.push(Buffer.alloc(i));
}
var ri=0;
var rj=0;
var wi=0;
var wj=0;
try {
 while(true) {
  mode2[wi][wj]=mode0[ri][rj];
  --ri;
  ++rj;
  ++wj;
  if(mode2[wi].length==wj) { //This bit is simple
   ++wi;
   wj=0;
  }
  if(ri<0) {
   ri=rj
   rj=0;
  }
  if(rj>=mode0.length) {
   ++ri; //Reverse
   --rj; //Reverse
   ++ri; //Go down one
   //Swap ri and rj
   var temp=ri;
   ri=rj;
   rj=temp;
  }
  if(ri>=mode0.length) {
   rj=(ri-(mode0.length-1));
   ri=mode0.length-1;
  }
 }
} catch(e) {
 //console.log('error',{ri,rj,wi,wj});
 //Let it run.  When we have an error we did the job
}

//Diagonal mode3
var mode3 = [];
for(var i=1;i<=width;++i) { //Allocate half
 mode3.push(Buffer.alloc(i));
}
for(var i=width-1;i>0;--i) { //Allocate second half
 mode3.push(Buffer.alloc(i));
}
var ri=0;
var rj=width-1;
var wi=0;
var wj=0;
try {
 while(true) {
  //console.log({ri,rj});
  mode3[wi][wj]=mode0[ri][rj];
  ++ri;
  ++rj;
  ++wj;
  if(mode3[wi].length==wj) { //This bit is simple
   ++wi;
   wj=0;
  }
  if(rj>=width) {
   --ri;//Reverse
   --rj;//Reverse
   ++ri;//Get on new diaganol
   rj=width-ri-1; // Go to other side of diaganol
   ri=0; // Go to other side of diaganol
  }
  if(rj<0) {
   ri=-rj;
   rj=0;
  }
  if(ri>=width) {
   --ri;//Reverse
   --rj;//Reverse
   --rj;//Get on new diaganol
   ri=width-1-rj;
   rj=0;
  }
  if(ri<0 || ri>=width || rj<0 || rj>=width) throw 'Out of bounds';
 }
} catch(e) {
 //console.log('Error mode3:',{ri,rj,wi,wj});
 //Continue, it is filled;
}


var modes = [mode0,mode1,mode2,mode3].map(i=>i.map(i=>i.toString())); //Convert all into strings
var regex1 = /XMAS/g
var regex2 = /SAMX/g

var sum = modes.reduce((acc1,grid)=>acc1+grid.reduce((acc2,line)=>{
 var match1 = line.match(regex1);
 var match2 = line.match(regex2);
 return acc2 + (match1?match1.length:0) + (match2?match2.length:0);
},0),0);

console.log('Result:',sum);