Lua银行家算法：资源分配的安全检查

local function need(maxs, alloc)
    local t = {}
    for i = 1, #maxs do
        t[i] = {}
        for j = 1, #maxs[i] do
            t[i][j] = maxs[i][j] - alloc[i][j]
        end
    end
    return t
end

local function isSafe(nd, alloc, avail)
    local n, done, work = #nd, {}, {}
    for j = 1, #avail do work[j] = avail[j] end
    local safe, moved = 0, true
    while safe < n and moved do
        moved = false
        for i = 1, n do
            if not done[i] then
                local ok = true
                for j = 1, #work do
                    if nd[i][j] > work[j] then
                        ok = false
                    end
                end
                if ok then
                    done[i] = true
                    safe = safe + 1
                    for j = 1, #alloc[i] do
                        work[j] = work[j] + alloc[i][j]
                    end
                    moved = true
                end
            end
        end
    end
    return safe == n
end