Spiral Memory - Advent of Code - 20171203

ac20171203.js

let findMoves = function(location) {
    let previousSquare = Math.floor(Math.sqrt(location));
    previousSquare = previousSquare % 2 == 0 ? previousSquare - 1 : previousSquare;
    let sideSize = previousSquare + 1;
    previousSquare *= previousSquare;
    console.log('debug', previousSquare, Math.floor(sideSize / 2), Math.floor((location - previousSquare) % (sideSize / 2)));

    return Math.floor(sideSize / 2) + Math.floor((location - previousSquare) % (sideSize / 2));
};


let test = 1;
let result = findMoves(test);
console.log(result);

test = 12;
result = findMoves(test);
console.log(result);

test = 23;
result = findMoves(test);
console.log(result);

test = 1024;
result = findMoves(test);
console.log(result);

test = 289326;
result = findMoves(test);
console.log(result);


let sumPoint = function(x, y, matrix) {
    let sum = 0;
    for (let i = x -1; i <= x + 1; i++) {
      if (matrix[i]) {
        for (let j = y -1; j <= y + 1; j++) {
          //console.log('sumPoint', i, j)
          if (matrix[i][j]) {
            sum += matrix[i][j];
          }
        }
      }
    }
    return sum;
};

let spiralExpand = function(location) {
  let previousSquare = Math.floor(Math.sqrt(location));
  previousSquare = previousSquare % 2 == 0 ? previousSquare - 1 : previousSquare;
  let size = previousSquare + 1;

  let length = Math.pow(size, 2);
  let matrix = new Array(size).fill(0);
  matrix = matrix.map(v => new Array(size).fill(0));

  let x = 0; // current position; x
  let y = 0; // current position; y
  let d = 0; // current direction; 0=RIGHT, 1=DOWN, 2=LEFT, 3=UP
  let c = 1; // counter
  let s = 1; // chain size

  let firstOver = -1;

  // starting point
  x = Math.floor(size / 2.0);
  y = Math.floor(size / 2.0);
  matrix[x][y] = 1;

  for (let k = 1; k <= size - 1; k++) {
    for (let j = 0; j < (k < size - 1 ? 2 : 3); j++) {
      for (let i = 0; i < s; i++) {
        matrix[x][y] = sumPoint(x, y, matrix);
        if (firstOver < 0 && matrix[x][y] > location) {
          firstOver = matrix[x][y];
          i = s;
          j = 4;
          k = size;
        }
        switch (d) {
          case 0:
            y = y + 1;
            break;
          case 1:
            x = x + 1;
            break;
          case 2:
            y = y - 1;
            break;
          case 3:
            x = x - 1;
            break;
        }
      }
      d = (d + 1) % 4;
    }
    s = s + 1;
  }
  return firstOver;
};

result = spiralExpand(test);
console.log(result);