How to iterate from last index to first in table - lua

Question

bestSword = {
{name = 'www' , lvl = 35, atk = 38, npcPrice = 15000 , buyPrice = 0},
{name = 'bbb' , lvl = 40, atk = 40, npcPrice = 20000 , buyPrice = 0},
{name = 'eee' , lvl = 50, atk = 42, npcPrice = 25000 , buyPrice = 0},
{name = 'sss' , lvl = 55, atk = 43, npcPrice = 30000 , buyPrice = 0},
{name = 'aaa' , lvl = 60, atk = 44, npcPrice = 30000 , buyPrice = 0},
{name = 'qwe' , lvl = 70, atk = 46, npcPrice = 35000 , buyPrice = 0},
{name = 'asd' , lvl = 82, atk = 48, npcPrice = 60000 , buyPrice = 0}
}
I have this table, how can I iterate from last index to first? It should break depends from lvl. I just want to show this table from the best weapon. For example if Player have level 53, then I want to show only weapons for his lvl or lower. I need to show that from the best one (at top) its why I want to iterate from the last index. Could someone help?
EDIT:
Thanks for help. There is still a problem that I need this changed table later. It shows all fine but I need to buy all litems from this (changed) list later. So I must replace in some way this 2 tables. Is there any easy way to do that? I tried to remove elements from this table but it still not works.
Or its possible to make some map in Lua? It must be dynamic sized so i cant use table i guess. Something with key - value

Answer 1

A numeric for loop, counting down, is the best option:
local t = {2,4,6,8}
for i = #t, 1, -1 do
print(t[i])
end

Answer 2

Assuming that the table is not necessarily sorted into level order (unlike the example), we need to do two things:
Find which swords are in the level range
Sort them into descending order
Now the first one in the temporary table is the "best" sword.
Like this:
bestSword = {
{name = 'www' , lvl = 35, atk = 38, npcPrice = 15000 , buyPrice = 0},
{name = 'bbb' , lvl = 40, atk = 40, npcPrice = 20000 , buyPrice = 0},
{name = 'eee' , lvl = 50, atk = 42, npcPrice = 25000 , buyPrice = 0},
{name = 'sss' , lvl = 55, atk = 43, npcPrice = 30000 , buyPrice = 0},
{name = 'aaa' , lvl = 60, atk = 44, npcPrice = 30000 , buyPrice = 0},
{name = 'qwe' , lvl = 70, atk = 46, npcPrice = 35000 , buyPrice = 0},
{name = 'asd' , lvl = 82, atk = 48, npcPrice = 60000 , buyPrice = 0}
}
myLevel = 53 -- wanted level
-- temporary table
possible = { }
-- extract ones which are in range
for k, v in ipairs (bestSword) do
if v.lvl <= myLevel then
table.insert (possible, v)
end -- if
end -- for
if #possible == 0 then
print "No matching swords"
else
table.sort (possible, function (a, b) return a.atk > b.atk end )
bestSword = possible [1]
print ("Best sword is", bestSword.name, "lvl =", bestSword.lvl,
"atk = ", bestSword.atk)
end -- if
Or its possible to make some map in Lua? It must be dynamic sized so i cant use table i guess. Something with key - value
Tables in Lua are maps. Every table has key/value pairs. The one you are using there are simply numerically-keyed tables.
All tables are dynamically sized.