【高级技巧】DFS先深搜索：连通区域的递归遍历封装

local function dfsMark(grid, x, y, visited, areaId)
    local key = x .. "," .. y
    if visited[key] then
        return 0
    end
    if grid[y] == nil or grid[y][x] == nil then
        return 0
    end
    if grid[y][x] ~= 1 then
        return 0
    end
    visited[key] = true
    local count = 1
    count = count + dfsMark(grid, x + 1, y, visited, areaId)
    count = count + dfsMark(grid, x - 1, y, visited, areaId)
    count = count + dfsMark(grid, x, y + 1, visited, areaId)
    count = count + dfsMark(grid, x, y - 1, visited, areaId)
    return count
end
local function findRegions(grid)
    local visited = {}
    local regions = {}
    for y = 1, #grid do
        for x = 1, #(grid[y] or {}) do
            local key = x .. "," .. y
            if not visited[key] and grid[y][x] == 1 then
                local size = dfsMark(grid, x, y, visited, #regions + 1)
                regions[#regions + 1] = size
            end
        end
    end
    return regions
end

print("DFS complete")