Advent of Code 2018: Day 11
SERIAL = 7139
GRIDSIZE = 300
Part 1 What is the X,Y coordinate of the top-left fuel cell of the 3x3 square with the largest total power?
function cellValue (x, y) { const gridId = x + 10; return Math.trunc((gridId * y + SERIAL) * gridId / 100) % 10 - 5; }
sumTable = { let out = Array(GRIDSIZE+1).fill().map(() => Array(GRIDSIZE+1).fill(0)); for (let x = GRIDSIZE; x > 0; x--) { for (let y = GRIDSIZE; y > 0; y--) { out[x-1][y-1] = cellValue(x, y) + out[x][y-1] + out[x-1][y] - out[x][y]; } } return out; }
function squareSubgridSum (x, y, w) { return sumTable[x-1][y-1] + sumTable[x+w-1][y+w-1] - sumTable[x-1][y+w-1] - sumTable[x+w-1][y-1]; }
function maxSquareSubgridByWidth (w) { let maxSum = 0; let maxX = 0; let maxY = 0; for (let x = 1; x <= GRIDSIZE - w; x++) { for (let y = 1; y <= GRIDSIZE - w; y++) { const sum = squareSubgridSum(x, y, w); if (sum > maxSum) { [maxSum, maxX, maxY] = [sum, x, y]; } } } return [maxX, maxY]; }
part1 = maxSquareSubgridByWidth(3).join(',')
Part 2 What is the X,Y,size identifier of the square with the largest total power?
function maxSquareSubgrid () { let maxSum = 0; let maxWidth = 0; let maxX = 0; let maxY = 0; for (let w = 1; w <= GRIDSIZE; w++) { for (let x = 1; x <= GRIDSIZE - w; x++) { for (let y = 1; y <= GRIDSIZE - w; y++) { const sum = squareSubgridSum(x, y, w); if (sum > maxSum) { [maxSum, maxWidth, maxX, maxY] = [sum, w, x, y]; } } } } return [maxX, maxY, maxWidth]; }
part2 = maxSquareSubgrid().join(',')