Lua验证回文串：双指针的首尾比对

local function isPalindrome(s)
    local clean = s:lower():gsub("%W", "")
    clean = clean:gsub("_", "")
    local left, right = 1, #clean
    while left < right do
        if clean:sub(left, left) ~= clean:sub(right, right) then
            return false
        end
        left = left + 1
        right = right - 1
    end
    return true
end

local function isAlnum(ch)
    return (ch >= "0" and ch <= "9")
        or (ch >= "a" and ch <= "z")
end
local function isPalindromeLive(s)
    s = s:lower()
    local left, right = 1, #s
    while left < right do
        while left < right and not isAlnum(s:sub(left, left)) do
            left = left + 1
        end
        while left < right and not isAlnum(s:sub(right, right)) do
            right = right - 1
        end
        if s:sub(left, left) ~= s:sub(right, right) then
            return false
        end
        left = left + 1
        right = right - 1
    end
    return true
end
local p = getplayerbyname("pal01")
sendmsg(p, 1, tostring(isPalindromeLive("A man, a plan, a canal: Panama")))