0200-number-of-islands.swift

classSolution{

func numIslands(_ grid:[[Character]])->Int{
letROWS= grid.count
letCOLS=grid[0].count

varvisited=[[Bool]](
 repeating:[Bool](repeating:false, count: COLS),
 count: ROWS
)
varcount:Int=0

 // Helper function to check if is within
func isWithin(row:Int, col:Int)->Bool{
return(
(row >=0) && (col >=0) &&
(row < ROWS) && (col < COLS)
)
}

 // Helper function to check if cell is land or not
func isLand(row:Int, col:Int)->Bool{
returngrid[row][col]=="1"
}

letmovementsX=[-1,1,0,0]
letmovementsY=[0,0,-1,1]

 // Helper DFS function to 'visit' the grid
func dfs(row:Int, col:Int){
 // visit each child
for(dirX, dirY)inzip(movementsX, movementsY){
letrowNew= row + dirX
letcolNew= col + dirY

guardisWithin(row: rowNew, col: colNew)else{continue}
guardvisited[rowNew][colNew]==falseelse{continue}
guardisLand(row: rowNew, col: colNew)else{continue}

visited[rowNew][colNew]=true
dfs(row: rowNew, col: colNew)
}
}

forrin0..<ROWS {
forcin0..<COLS {
guardvisited[r][c]==falseelse{continue}
guardisLand(row: r, col: c)else{continue}

visited[r][c]=true
dfs(row: r, col: c)
 count +=1
}
}

return count
}
}