【Lua实战】广度优先搜索：传送点最短路径计算

local PORTALS = {
    ["比奇省"]   = { "盟重土城", "白日门" },
    ["盟重土城"] = { "白日门", "沙巴克" },
    ["白日门"]   = { "封魔谷" },
    ["封魔谷"]   = { "沙巴克" },
    ["沙巴克"]   = {},
}
local function shortestPath(start, goal)
    local queue = { { start } }
    local seen = { [start] = true }
    while #queue > 0 do
        local path = table.remove(queue, 1)
        local cur = path[#path]
        if cur == goal then return path end
        for _, next in ipairs(PORTALS[cur] or {}) do
            if not seen[next] then
                seen[next] = true
                local copy = {}
                for i, v in ipairs(path) do copy[i] = v end
                table.insert(copy, next)
                table.insert(queue, copy)
            end
        end
    end
    return nil
end

local function showRoute(actor, goal)
    local path = shortestPath("比奇省", goal)
    if path == nil then
        sendmsg(actor, 0, "未找到通往 " .. goal .. " 的传送路线")
        return
    end
    sendmsg(actor, 0, "推荐路线：" .. table.concat(path, " → "))
end