【高级技巧】位图法：海量数据的去重存储封装

local bits = {}
local function setBit(pos)
    local cell = math.floor(pos / 32) + 1
    local off = 2 ^ (pos % 32)
    local cur = bits[cell] or 0
    if math.floor(cur / off) % 2 == 0 then
        bits[cell] = cur + off
    end
end
local function getBit(pos)
    local cell = math.floor(pos / 32) + 1
    local off = 2 ^ (pos % 32)
    return math.floor((bits[cell] or 0) / off) % 2
end
local function isDuplicate(playerId)
    if getBit(playerId) == 1 then
        return true
    end
    setBit(playerId)
    return false
end

print(isDuplicate(12345))
print(isDuplicate(12345))