Lua接雨水：双指针的积水计算

local function trapSlow(h)
    local total = 0
    for i = 1, #h do
        local lmax, rmax = 0, 0
        for j = 1, i do lmax = math.max(lmax, h[j]) end
        for j = i, #h do rmax = math.max(rmax, h[j]) end
        total = total + math.min(lmax, rmax) - h[i]
    end
    return total
end

local function trap(h)
    local l, r = 1, #h
    local lmax, rmax, total = 0, 0, 0
    while l <= r do
        if h[l] <= h[r] then
            lmax = math.max(lmax, h[l])
            total = total + lmax - h[l]
            l = l + 1
        else
            rmax = math.max(rmax, h[r])
            total = total + rmax - h[r]
            r = r - 1
        end
    end
    return total
end
local p = getplayerbyname("rain01")
sendmsg(p, 1, "积水 " .. trap({2, 0, 3, 0, 4}))