【高级技巧】单调栈：下一个更大元素的线性解

local function nextGreater(nums)
    local result = {}
    local stack = {}
    for i = 1, #nums do
        result[i] = -1
    end
    for i = 1, #nums do
        while #stack > 0 and nums[i] > nums[stack[#stack]] do
            local j = stack[#stack]
            table.remove(stack)
            result[j] = nums[i]
        end
        stack[#stack + 1] = i
    end
    return result
end
print(table.concat(nextGreater({ 2, 7, 3, 9, 5 }), ","))

local bids = { 120, 250, 180, 400 }
print(table.concat(nextGreater(bids), ","))