Lua异或消除：成对编号中找落单值

local function single(t)
    local seen = {}
    for _, v in ipairs(t) do
        seen[v] = not seen[v]       -- 翻转标记，还得再扫一遍
    end
    for k, v in pairs(seen) do
        if v then return k end
    end
end

local function xor(a, b)
    local r, bit = 0, 1
    while a > 0 or b > 0 do
        if a % 2 ~= b % 2 then
            r = r + bit             -- 该位不同则置1
        end
        a = math.floor(a / 2)
        b = math.floor(b / 2)
        bit = bit * 2
    end
    return r
end
local function single(t)
    local r = 0
    for _, v in ipairs(t) do
        r = xor(r, v)               -- 连消成对，剩落单
    end
    return r
end
sendmsg(actor, 1, "落单编号 " .. single({7, 3, 9, 3, 7}))