AoC 2021 D25: Sea Cucumber

TypeScript | Problem statement | Source code | Tags: Cellular automata

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I thought this requires something clever, but simulating it straightforwardly is fast enough. For example, this is the code for moving the east-facing cucumbers:

function moveEast(mat: string[][]) {
  const newMat = mat.map((line) => line.slice());
  for (let row = 0; row < mat.length; row++) {
    for (let col = 0; col < mat[0].length; col++) {
      if (
        mat[row][col] === ">" &&
        mat[row][(col + 1) % mat[0].length] === "."
      ) {
        newMat[row][(col + 1) % mat[0].length] = ">";
        newMat[row][col] = ".";
      }
    }
  }
  return newMat;
}
ts

Checking for stabilization is done with a tiny trick: JSON.stringify(mat) === JSON.stringify(newMat2).

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