Lua双指针：回文串的首尾夹逼判定

local function isPalin(s)
    local r = string.reverse(s)    -- 反转整串多花一份内存
    return s == r
end

local function isPalin(s)
    local i, j = 1, #s
    while i < j do
        if string.byte(s, i) ~= string.byte(s, j) then
            return false
        end
        i, j = i + 1, j - 1        -- 首尾夹逼
    end
    return true
end
sendmsg(actor, 1, "回文判定："
    .. tostring(isPalin("abc cba")))