Lua全排列：递归交换的排列枚举

local perms = {}
for a = 1, 3 do
    for b = 1, 3 do
        for c = 1, 3 do
            perms[#perms + 1] = {a, b, c}   -- 27种含重复，非排列
        end
    end
end

local perms = {}
local function perm(t, i)
    if i > #t then
        perms[#perms + 1] = table.concat(t, ",")
        return
    end
    for j = i, #t do
        t[i], t[j] = t[j], t[i]     -- 换位固定第i位
        perm(t, i + 1)
        t[i], t[j] = t[j], t[i]     -- 回溯恢复现场
    end
end
perm({"金", "银", "铜"}, 1)
sendmsg(actor, 1, "摆放全排列 " .. #perms .. " 种")