Lua并查集：分组合并的路径压缩

-- 错误：合并即全组改号，组大时写入爆炸
function mergeGroup(a, b)
    for i, g in pairs(groupOf) do
        if g == groupOf[b] then
            groupOf[i] = groupOf[a]
        end
    end
end

local parent = {}
local function find(x)
    while parent[x] ~= x do
        parent[x] = parent[parent[x]]
        x = parent[x]
    end
    return x
end
local function union(a, b)
    local ra, rb = find(a), find(b)
    if ra ~= rb then
        parent[rb] = ra
    end
end
for i = 1, 8 do parent[i] = i end
union(1, 2); union(2, 3)
local p = getplayerbyname("unf01")
sendmsg(p, 1, "1 与 3 同组：" .. tostring(find(1) == find(3)))