for i=1, n do
   for j=1, m do
      if(j~=m) then  io.write(arr[i][j].." ")
      else print(arr[i][j])
      end
   end
end

local l = list
while l do
    print(l.value)
    l = l.next
end

function List.new()
   return {first=0, last=-1}
end

function List.pushFront(list,value)
   list.first=list.first-1
   list[ list.first ]=value
end

function List.pushBack(list,value)
   list.last=list.last+1
   list[ list.last ]=value
end

function List.popFront(list)
   local first=list.first
   if first>list.last then error("List is empty!")
   end
   local value =list[first]
   list[first]=nil
   list.first=first+1
   return value
end

function List.popBack(list)
   local last=list.last
   if last<list.first then error("List is empty!")
   end
   local value =list[last]
   list[last]=nil
   list.last=last-1
   return value
end

lp=List.new()
List.pushFront(lp,1)
List.pushFront(lp,2)
List.pushBack(lp,-1)
List.pushBack(lp,-2)
x=List.popFront(lp)
print(x)
x=List.popBack(lp)
print(x)
x=List.popFront(lp)
print(x)
x=List.popBack(lp)
print(x)
x=List.popBack(lp)
print(x)
--輸出結果
-- 2
-- -2
-- 1
-- -1
-- lua：... List is empty！

function remove(Bag,element)
   local count=Bag[element]
   if count >0 then Bag[element]=count-1
   else Bag[element]=nil
   end
end

for line in io.lines() do
   if(line==nil) then break end
   t[#t+1]=line
end

local s=table.concat(t,"\n")  --將table t 中的字符串連接起來