Function removeIslands

matrix/remove-islands.js:73–101

(matrix)

*/

function removeIslands(matrix) {
  // 1 -- change ones connected to border to twos '2'

  for (let row = 0; row < matrix.length; row++) {
    for (let col = 0; col < matrix[row].length; col++) {
      const rowIsBorder = row === 0 || row === matrix.length - 1;
      const colIsBorder = col === 0 || col === matrix[row].length - 1;
      const isBorder = rowIsBorder || colIsBorder;
      if (!isBorder) continue;
      if (matrix[row][col] !== 1) continue;
      changeOnesConnectedToBorderToTwos(matrix, row, col);
    }
  }

  // 2 -- change '2' to '1' and '1' to '0';

  for (let row = 0; row < matrix.length; row++) {
    for (let col = 0; col < matrix[row].length; col++) {
      const color = matrix[row][col];
      if (color === 1) {
        matrix[row][col] = 0;
      } else if (color === 2) {
        matrix[row][col] = 1;
      }
    }
  }

  return matrix;
}

function changeOnesConnectedToBorderToTwos(matrix, startRow, startCol) {
  const stack = [[startRow, startCol]];