剑指 Offer II 105. 岛屿的最大面积

var n,m,ans int
var dir =[][]int{{1,0},{0,1},{-1,0},{0,-1}}
func checkRange(x,y int) bool{
    if x>=0&&x<n&&y>=0&&y<m{
        return true
    }
    return false
}
func dfs(x,y int,grid [][]int) int{
    if checkRange(x,y)&&grid[x][y]==1{
        ans++
        grid[x][y]=0
    }
    for i:=0;i<4;i++{
        dx:=x+dir[i][0]
        dy:=y+dir[i][1]
        if checkRange(dx,dy)&&grid[dx][dy]==1{
            dfs(dx,dy,grid)
        }
    }
    return ans
}
func maxAreaOfIsland(grid [][]int) int {
    n=len(grid);m=len(grid[0])
    mxAns:=0
    for i:=0;i<n;i++{
        for j:=0;j<m;j++{
            if grid[i][j]==0{
                continue
            }
            ans=0
            mxAns=getMax(mxAns,dfs(i,j,grid))
        }
    }
    return mxAns
}
func getMax(a,b int)int{
    if a>b{
        return a
    }
    return b
}