【性能调优】掉落物归并：同屏掉落的合并拾取

-- 掉落物归并：区域聚类
local player = class(actor)
local piles = {}
local RADIUS = 5
local RARE_QUALITY = 4
local function dropLoot(player, itemName, quality, x, y)
    if quality >= RARE_QUALITY then
        throwitem(player, itemName)
        return
    end
    for _, pile in ipairs(piles) do
        if pile.item == itemName and math.abs(pile.x - x) <= RADIUS
            and math.abs(pile.y - y) <= RADIUS then
            pile.count = pile.count + 1
            return
        end
    end
    piles[#piles + 1] = {item = itemName, x = x, y = y, count = 1}
end

-- 掉落物归并：拾取拆分
local player = class(actor)
local function pickPile(player, pileIdx)
    local pile = piles[pileIdx]
    if pile == nil then return end
    giveitem(player, pile.item, pile.count)
    sendmsg(player, 1, 0, "拾取 " .. pile.item .. " x" .. pile.count .. "。")
    table.remove(piles, pileIdx)
    for i = pileIdx, #piles do
        piles[i] = piles[i + 1]
    end
end