011.js

/* eslint-disable max-len */

console.time('11');
const grid = [
  [8, 2, 22, 97, 38, 15, 0, 40, 0, 75, 4, 5, 7, 78, 52, 12, 50, 77, 91, 8],
  [
    49,
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    18,
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    87,
    17,
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    62,
    0,
  ],
  [
    81,
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    31,
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    14,
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    30,
    3,
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    13,
    36,
    65,
  ],
  [52, 70, 95, 23, 4, 60, 11, 42, 69, 24, 68, 56, 1, 32, 56, 71, 37, 2, 36, 91],
  [
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  ],
  [
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  [
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  ],
  [21, 36, 23, 9, 75, 0, 76, 44, 20, 45, 35, 14, 0, 61, 33, 97, 34, 31, 33, 95],
  [78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 3, 80, 4, 62, 16, 14, 9, 53, 56, 92],
  [
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  ],
  [86, 56, 0, 48, 35, 71, 89, 7, 5, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58],
  [
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  ],
  [4, 52, 8, 83, 97, 35, 99, 16, 7, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66],
  [
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  ],
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  [
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  ],
  [
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  ],
  [1, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 1, 89, 19, 67, 48],
];
const get4down = (y, x) => grid[y][x] * grid[y + 1][x] * grid[y + 2][x] * grid[y + 3][x];
const get4right = (y, x) => grid[y][x] * grid[y][x + 1] * grid[y][x + 2] * grid[y][x + 3];
const get4diagr = (y, x) => grid[y][x] * grid[y + 1][x + 1] * grid[y + 2][x + 2] * grid[y + 3][x + 3];
const get4diagl = (y, x) => grid[y][x] * grid[y + 1][x - 1] * grid[y + 2][x - 2] * grid[y + 3][x - 3];
const maxY = 20;
const maxX = 20;
let result = 0;
for (let y = 0; y < maxY; y += 1) {
  for (let x = 0; x < maxX; x += 1) {
    const down = y <= maxY - 4 ? get4down(y, x) : 0;
    const right = x <= maxX - 4 ? get4right(y, x) : 0;
    const diagr = y <= maxY - 4 && x <= maxX - 4 ? get4diagr(y, x) : 0;
    const diagl = y <= maxY - 4 && x >= 3 ? get4diagl(y, x) : 0;
    result = Math.max(result, down, right, diagr, diagl);
  }
}
console.log(result);
console.timeEnd('11');