Lua三数之和：排序加双指针的三元组

local function threeSumSlow(nums)
    table.sort(nums)
    local out = {}
    for i = 1, #nums - 2 do
        for j = i + 1, #nums - 1 do
            for k = j + 1, #nums do
                if nums[i] + nums[j] + nums[k] == 0 then
                    local key = nums[i] .. nums[j] .. nums[k]
                    if out[#out] ~= key then
                        out[#out + 1] = key
                    end
                end
            end
        end
    end
    return out
end

local function threeSum(nums)
    table.sort(nums)
    local out = {}
    for i = 1, #nums - 2 do
        if i == 1 or nums[i] ~= nums[i - 1] then
            local lo, hi = i + 1, #nums
            while lo < hi do
                local s = nums[i] + nums[lo] + nums[hi]
                if s == 0 then
                    out[#out + 1] = nums[i] .. ","
                        .. nums[lo] .. "," .. nums[hi]
                    lo = lo + 1
                    hi = hi - 1
                elseif s < 0 then lo = lo + 1
                else hi = hi - 1 end
            end
        end
    end
    return out
end
local p = getplayerbyname("ts01")
sendmsg(p, 1, table.concat(
    threeSum({-1, 0, 1, 2, -1, -4}), " / "))