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Challenge 125: Game of Life

curriculum/challenges/english/blocks/daily-coding-challenges-javascript/691b559495c5cb5a37b9b485.md

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--description--

Given a matrix (array of arrays) representing the current state in Conway's Game of Life, return the next state of the matrix using these rules:

  • Each cell is either 1 (alive) or 0 (dead).
  • A cell's neighbors are the up to eight surrounding cells (vertically, horizontally, and diagonally).
  • Cells on the edges have fewer than eight neighbors.

Rules for updating each cell:

  • Any live cell with fewer than two live neighbors dies (underpopulation).
  • Any live cell with two or three live neighbors lives on.
  • Any live cell with more than three live neighbors dies (overpopulation).
  • Any dead cell with exactly three live neighbors becomes alive (reproduction).

For example, given:

json
[
  [0, 1, 0],
  [0, 1, 1],
  [1, 1, 0]
]

return:

json
[
  [0, 1, 1],
  [0, 0, 1],
  [1, 1, 1]
]

Each cell updates according to the number of live neighbors. For instance, [0][0] stays dead (2 live neighbors), [0][1] stays alive (2 live neighbors), [0][2] dies (3 live neighbors), and so on.

--hints--

gameOfLife([[0, 1, 0], [0, 1, 1], [1, 1, 0]]) should return [[0, 1, 1], [0, 0, 1], [1, 1, 1]].

js
assert.deepEqual(gameOfLife([[0, 1, 0], [0, 1, 1], [1, 1, 0]]), [[0, 1, 1], [0, 0, 1], [1, 1, 1]]);

gameOfLife([[1, 1, 0, 0], [1, 0, 1, 0], [0, 1, 1, 1], [0, 0, 1, 0]]) should return [[1, 1, 0, 0], [1, 0, 0, 1], [0, 0, 0, 1], [0, 1, 1, 1]].

js
assert.deepEqual(gameOfLife([[1, 1, 0, 0], [1, 0, 1, 0], [0, 1, 1, 1], [0, 0, 1, 0]]), [[1, 1, 0, 0], [1, 0, 0, 1], [0, 0, 0, 1], [0, 1, 1, 1]]);

gameOfLife([[1, 0, 0], [0, 1, 0], [0, 0, 1]]) should return [[0, 0, 0], [0, 1, 0], [0, 0, 0]].

js
assert.deepEqual(gameOfLife([[1, 0, 0], [0, 1, 0], [0, 0, 1]]), [[0, 0, 0], [0, 1, 0], [0, 0, 0]]);

gameOfLife([[0, 1, 1, 0], [1, 1, 0, 1], [0, 1, 1, 0], [0, 0, 1, 0]]) should return [[1, 1, 1, 0], [1, 0, 0, 1], [1, 0, 0, 1], [0, 1, 1, 0]].

js
assert.deepEqual(gameOfLife([[0, 1, 1, 0], [1, 1, 0, 1], [0, 1, 1, 0], [0, 0, 1, 0]]), [[1, 1, 1, 0], [1, 0, 0, 1], [1, 0, 0, 1], [0, 1, 1, 0]]);

--seed--

--seed-contents--

js
function gameOfLife(grid) {
  return grid;
}

--solutions--

js
function gameOfLife(grid) {
  const rows = grid.length;
  const cols = grid[0].length;

  const countLiveNeighbors = (r, c) => {
    let count = 0;
    for (let i = r - 1; i <= r + 1; i++) {
      for (let j = c - 1; j <= c + 1; j++) {
        if (
          i >= 0 &&
          i < rows &&
          j >= 0 &&
          j < cols &&
          !(i === r && j === c) &&
          grid[i][j] === 1
        ) {
          count++;
        }
      }
    }
    return count;
  };

  const next = grid.map(row => [...row]);

  for (let r = 0; r < rows; r++) {
    for (let c = 0; c < cols; c++) {
      const liveNeighbors = countLiveNeighbors(r, c);

      if (grid[r][c] === 1) {
        if (liveNeighbors < 2 || liveNeighbors > 3) next[r][c] = 0;
      } else {
        if (liveNeighbors === 3) next[r][c] = 1;
      }
    }
  }

  return next;
}