【入门夯实】表转树：扁平配置构造层级结构

local rows = {
    { id = 1, name = "会长", pid = 0 },
    { id = 2, name = "长老", pid = 1 },
    { id = 3, name = "精英", pid = 1 },
}
for _, r in ipairs(rows) do
    local parent = tree[r.pid]
    table.insert(parent.children, r)
end

local function buildTree(rows)
    local index = {}
    for _, r in ipairs(rows) do
        index[r.id] = { id = r.id, name = r.name, children = {} }
    end
    local roots = {}
    for _, r in ipairs(rows) do
        if r.pid == 0 then
            roots[#roots + 1] = index[r.id]
        else
            local parent = index[r.pid]
            if parent then
                table.insert(parent.children, index[r.id])
            end
        end
    end
    return roots, index
end

local roots, index = buildTree(rows)
sendmsg(nil, 1, "根节点：" .. roots[1].name .. "，下属 " .. #roots[1].children .. " 类")

local function flatten(node, depth, out)
    out[#out + 1] = string.rep("  ", depth) .. node.name
    for _, c in ipairs(node.children) do
        flatten(c, depth + 1, out)
    end
end