Number of Islands - JavaScript

number-of-islands.js

const numIslands = grid => {
  // need variable to count islands
  let islands = 0
  
  // create a function to search for 1 and use recursion to search surrounding cells
  const findIslands = (row, col, grid) => {
    // first check if row and col exist on grid and if grid[row][col] 0
    if (
      row < 0 || 
      col < 0 || 
      row > grid.length - 1 || 
      col > grid[row].length - 1 || 
      grid[row][col] === '0'
    ) {
      return
    }
    
    // use recursion to search surrounding cells
    grid[row][col] = '0'
    findIslands(row - 1, col, grid)
    findIslands(row, col - 1, grid)
    findIslands(row + 1, col, grid)
    findIslands(row, col + 1, grid)
  }
  
  // use forEach to loop through grid and use findIslands function
  grid.forEach((row, index) => {
    row.forEach((value, i) => {
      // check if value === '1' and if so, use findIslands to check surrounding cells
      if (value === '1') {
        findIslands(index, i, grid)
        islands ++
      }
    })
  })
  
  // return number of islands
  return islands
};