Day10 part1.js

const fs = require('fs')
const path = require('path')
const data = fs.readFileSync(path.join(__dirname, 'input.txt'), 'utf-8')
const rows = data.split('\n').filter(r => r !== '')

const matrix = rows.map(row => {
  return row.split('').map(cell => {
    if (cell === '.') {
      return '.'
    }
    return 0
  })
})
function part1(matrix) {
  let max = Number.MIN_SAFE_INTEGER
  let maxPoint = {}
  matrix.forEach((row, rowIndex) => {
    row.forEach((cell, colIndex) => {
      if (cell !== '.') {
        let angleCount = computeAnglesForCell(matrix, { x: rowIndex, y: colIndex })
        matrix[rowIndex][colIndex] = angleCount
        if (angleCount > max) {
          max = angleCount
          maxPoint = { x: rowIndex, y: colIndex }
        }
      }
    })
  })
  return {
    max,
    maxPoint
  }
}

function computeAnglesForCell(matrix, cellCoords) {
  let anglesSet = new Set()
  matrix.forEach((row, rowIndex) => {
    row.forEach((cell, colIndex) => {
      if (cell !== '.') {
        const p1 = { x: rowIndex, y: colIndex }
        let angle = getAngle(p1, cellCoords)
        if (cellCoords.x === rowIndex && colIndex === cellCoords.y) {
          // skip same cell
        } else {
          anglesSet.add(angle)
        }
      }
    })
  })
  return anglesSet.size
}

function getAngle(p1, p2) {
  return Math.atan2(p2.y - p1.y, p2.x - p1.x) * 180 / Math.PI;
}
let { maxPoint, max } = part1(matrix)
console.log(maxPoint, max)